feat: Add option to delete a application snapshot (#21216)

## Description
This PR adds the option to delete an application snapshot in the
following cases:
    
- A DELETE API that'll delete an application snapshot
- The restore API should delete the underlying application snapshot if
the restore is successful



Fixes #21215


Media
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## Type of change

> Please delete options that are not relevant.

- Chore (housekeeping or task changes that don't impact user perception)


## How Has This Been Tested?
> Please describe the tests that you ran to verify your changes. Provide
instructions, so we can reproduce.
> Please also list any relevant details for your test configuration.
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- Manual
- JUnit tests

### Test Plan
> Add Testsmith test cases links that relate to this PR

### Issues raised during DP testing
> Link issues raised during DP testing for better visiblity and tracking
(copy link from comments dropped on this PR)


## Checklist:
### Dev activity
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my own code
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] PR is being merged under a feature flag


### QA activity:
- [ ] Test plan has been approved by relevant developers
- [ ] Test plan has been peer reviewed by QA
- [ ] Cypress test cases have been added and approved by either SDET or
manual QA
- [ ] Organized project review call with relevant stakeholders after
Round 1/2 of QA
- [ ] Added Test Plan Approved label after reveiwing all Cypress test

app/server/appsmith-server/src/main/java/com/appsmith/server/controllers/ce/ApplicationControllerCE.java

@@ -201,6 +201,14 @@ public class ApplicationControllerCE extends BaseController<ApplicationService,
                 .map(applicationSnapshot -> new ResponseDTO<>(HttpStatus.OK.value(), applicationSnapshot, null));
     }
 
+    @DeleteMapping("/snapshot/{id}")
+    public Mono<ResponseDTO<Boolean>> deleteSnapshotWithoutApplicationJson(@PathVariable String id, @RequestHeader(name = FieldName.BRANCH_NAME, required = false) String branchName) {
+        log.debug("Going to delete snapshot with application id: {}, branch: {}", id, branchName);
+
+        return applicationSnapshotService.deleteSnapshot(id, branchName)
+                .map(isDeleted -> new ResponseDTO<>(HttpStatus.OK.value(), isDeleted, null));
+    }
+
     @PostMapping("/snapshot/{id}/restore")
     public Mono<ResponseDTO<Application>> restoreSnapshot(@PathVariable String id, @RequestHeader(name = FieldName.BRANCH_NAME, required = false) String branchName) {
         log.debug("Going to restore snapshot with application id: {}, branch: {}", id, branchName);

app/server/appsmith-server/src/main/java/com/appsmith/server/services/ce/ApplicationSnapshotServiceCE.java

@@ -17,4 +17,6 @@ public interface ApplicationSnapshotServiceCE {
     Mono<ApplicationSnapshot> getWithoutDataByApplicationId(String applicationId, String branchName);
 
     Mono<Application> restoreSnapshot(String applicationId, String branchName);
+
+    Mono<Boolean> deleteSnapshot(String applicationId, String branchName);
 }

app/server/appsmith-server/src/main/java/com/appsmith/server/services/ce/ApplicationSnapshotServiceCEImpl.java

@@ -91,7 +91,11 @@ public class ApplicationSnapshotServiceCEImpl implements ApplicationSnapshotServ
                     return importExportApplicationService.importApplicationInWorkspace(
                             application.getWorkspaceId(), applicationJson, application.getId(), branchName
                     );
-                });
+                })
+                .flatMap(application ->
+                    applicationSnapshotRepository.deleteAllByApplicationId(application.getId())
+                            .thenReturn(application)
+                );
     }
 
     private Mono<String> getApplicationJsonStringFromSnapShot(String applicationId) {
@@ -134,4 +138,16 @@ public class ApplicationSnapshotServiceCEImpl implements ApplicationSnapshotServ
         }
         return applicationSnapshots;
     }
+
+    @Override
+    public Mono<Boolean> deleteSnapshot(String applicationId, String branchName) {
+        // find root application by applicationId and branchName
+        return applicationService.findBranchedApplicationId(branchName, applicationId, applicationPermission.getEditPermission())
+                .switchIfEmpty(Mono.error(
+                        new AppsmithException(AppsmithError.NO_RESOURCE_FOUND, FieldName.APPLICATION, applicationId))
+                )
+                .flatMap(branchedAppId ->
+                        applicationSnapshotRepository.deleteAllByApplicationId(branchedAppId).thenReturn(Boolean.TRUE)
+                );
+    }
 }

app/server/appsmith-server/src/test/java/com/appsmith/server/services/ApplicationSnapshotServiceTest.java

@@ -18,6 +18,7 @@ import reactor.test.StepVerifier;
 import reactor.util.function.Tuple2;
 
 import java.nio.charset.StandardCharsets;
+import java.util.List;
 import java.util.UUID;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -210,8 +211,8 @@ public class ApplicationSnapshotServiceTest {
             pageDTO.setApplicationId(application.getId());
             return applicationPageService.createPage(pageDTO)
                     .then(applicationSnapshotService.restoreSnapshot(application.getId(), null))
-                    .then(newPageService.findApplicationPages(application.getId(), null, null, ApplicationMode.EDIT));
-        });
+                .then(newPageService.findApplicationPages(application.getId(), null, null, ApplicationMode.EDIT));
+    });
 
         // not using Mono.zip because we want pagesBeforeSnapshot to finish first
         Mono<Tuple2<ApplicationPagesDTO, ApplicationPagesDTO>> tuple2Mono = pagesBeforeSnapshot
@@ -225,4 +226,50 @@ public class ApplicationSnapshotServiceTest {
             })
             .verifyComplete();
     }
+
+    @Test
+    @WithUserDetails("api_user")
+    public void restoreSnapshot_WhenSuccessfullyRestored_SnapshotDeleted() {
+        String uniqueString = UUID.randomUUID().toString();
+
+        // create a new workspace
+        Workspace workspace = new Workspace();
+        workspace.setName("Test workspace " + uniqueString);
+
+        Flux<ApplicationSnapshot> snapshotFlux = workspaceService.create(workspace)
+                .flatMap(createdWorkspace -> {
+                    Application testApplication = new Application();
+                    testApplication.setName("App before snapshot");
+                    return applicationPageService.createApplication(testApplication, workspace.getId());
+                }).flatMap(application -> { // create a snapshot
+                    return applicationSnapshotService.createApplicationSnapshot(application.getId(), null)
+                            .thenReturn(application);
+                })
+                .flatMapMany(application ->
+                        applicationSnapshotService.restoreSnapshot(application.getId(), null)
+                                .thenMany(applicationSnapshotRepository.findByApplicationId(application.getId()))
+                );
+
+        StepVerifier.create(snapshotFlux)
+                .verifyComplete();
+    }
+
+    @Test
+    public void deleteSnapshot_WhenSnapshotExists_Deleted() {
+        String testAppId = "app-" + UUID.randomUUID().toString();
+        ApplicationSnapshot snapshot1 = new ApplicationSnapshot();
+        snapshot1.setChunkOrder(1);
+        snapshot1.setApplicationId(testAppId);
+
+        ApplicationSnapshot snapshot2 = new ApplicationSnapshot();
+        snapshot2.setApplicationId(testAppId);
+        snapshot2.setChunkOrder(2);
+
+        Flux<ApplicationSnapshot> snapshotFlux = applicationSnapshotRepository.saveAll(List.of(snapshot1, snapshot2))
+                .then(applicationSnapshotService.deleteSnapshot(testAppId, null))
+                .thenMany(applicationSnapshotRepository.findByApplicationId(testAppId));
+
+        StepVerifier.create(snapshotFlux)
+                .verifyComplete();
+    }
 }

app/server/appsmith-server/src/test/java/com/appsmith/server/services/ce/ApplicationSnapshotServiceUnitTest.java

@@ -134,6 +134,9 @@ public class ApplicationSnapshotServiceUnitTest {
         Mockito.when(importExportApplicationService.importApplicationInWorkspace(eq(application.getWorkspaceId()), argThat(matchApplicationJson), eq(branchedAppId), eq(branch)))
                 .thenReturn(Mono.just(application));
 
+        Mockito.when(applicationSnapshotRepository.deleteAllByApplicationId(branchedAppId))
+                .thenReturn(Mono.just("application").then());
+
         StepVerifier.create(applicationSnapshotService.restoreSnapshot(defaultAppId, branch))
                 .assertNext(application1 -> {
                     assertThat(application1.getName()).isEqualTo(application.getName());