chore: Refactor UpdateSuperUserMigrationHelperCE for re-use in EE (#36851)

## Automation

/ok-to-test tags="@tag.Sanity"

### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results  -->
> [!TIP]
> 🟢 🟢 🟢 All cypress tests have passed! 🎉 🎉 🎉
> Workflow run:
<https://github.com/appsmithorg/appsmith/actions/runs/11321563633>
> Commit: 402dfb3ae87383f87afc5b343971e5334b79a695
> <a
href="https://internal.appsmith.com/app/cypress-dashboard/rundetails-65890b3c81d7400d08fa9ee5?branch=master&workflowId=11321563633&attempt=2"
target="_blank">Cypress dashboard</a>.
> Tags: `@tag.Sanity`
> Spec:
> <hr>Mon, 14 Oct 2024 06:12:25 UTC
<!-- end of auto-generated comment: Cypress test results  -->


## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [ ] No


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Enhanced user creation process with automatic generation of user
management permission groups and policies.
- Introduced a new method for creating permission groups associated with
user management.

- **Bug Fixes**
	- Streamlined the assignment of user policies during user creation.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

app/server/appsmith-server/src/main/java/com/appsmith/server/migrations/solutions/ce/UpdateSuperUserMigrationHelperCE.java

@@ -8,6 +8,7 @@ import com.appsmith.server.domains.Tenant;
 import com.appsmith.server.domains.User;
 import com.appsmith.server.dtos.Permission;
 import com.appsmith.server.solutions.PolicySolution;
+import org.jetbrains.annotations.NotNull;
 import org.springframework.data.mongodb.core.MongoTemplate;
 
 import java.time.Instant;
@@ -56,7 +57,17 @@ public class UpdateSuperUserMigrationHelperCE {
         user.setCreatedAt(Instant.now());
         user = mongoTemplate.save(user);
 
-        // Assign the user to the default permissions
+        PermissionGroup userManagementPermissionGroup = createUserManagementPermissionGroup(mongoTemplate, user);
+
+        Set<Policy> userPolicies = this.generateUserPolicy(
+                user, userManagementPermissionGroup, instanceAdminRole, tenant, policySolution, policyGenerator);
+
+        user.setPolicies(userPolicies);
+
+        return mongoTemplate.save(user);
+    }
+
+    @NotNull public static PermissionGroup createUserManagementPermissionGroup(MongoTemplate mongoTemplate, User user) {
         PermissionGroup userManagementPermissionGroup = new PermissionGroup();
         userManagementPermissionGroup.setName(user.getUsername() + FieldName.SUFFIX_USER_MANAGEMENT_ROLE);
         // Add CRUD permissions for user to the group
@@ -66,12 +77,6 @@ public class UpdateSuperUserMigrationHelperCE {
         userManagementPermissionGroup.setAssignedToUserIds(Set.of(user.getId()));
 
         PermissionGroup savedPermissionGroup = mongoTemplate.save(userManagementPermissionGroup);
-
-        Set<Policy> userPolicies = this.generateUserPolicy(
-                user, savedPermissionGroup, instanceAdminRole, tenant, policySolution, policyGenerator);
-
-        user.setPolicies(userPolicies);
-
-        return mongoTemplate.save(user);
+        return savedPermissionGroup;
     }
 }