test: Add AssertJ for plugins, for better assertions (#31380)

PR adds assertj to the plugin modules as well so we can write better
assertions there. We're changing just one test, but to illustrate as an
example.

With the previous assertion used here, failure messages looked like
this:

```
Expected <true>, but got <false>.
```

But with the better assertions introduced in this PR, we should see
something like:

```
Expected `Random unexpected string` to end with `Host not allowed.`
```

Which should help us much better in troubleshooting.

app/server/appsmith-plugins/pom.xml

@@ -5,136 +5,79 @@
     <modelVersion>4.0.0</modelVersion>
 
     <parent>
-
         <groupId>com.appsmith</groupId>
-
         <artifactId>integrated</artifactId>
-
         <version>1.0-SNAPSHOT</version>
-
     </parent>
 
     <artifactId>appsmith-plugins</artifactId>
-
     <version>1.0-SNAPSHOT</version>
-
     <packaging>pom</packaging>
 
     <modules>
-
         <module>oraclePlugin</module>
-
         <module>postgresPlugin</module>
-
         <module>restApiPlugin</module>
-
         <module>mongoPlugin</module>
-
         <module>mysqlPlugin</module>
-
         <module>elasticSearchPlugin</module>
-
         <module>dynamoPlugin</module>
-
         <module>redisPlugin</module>
-
         <module>mssqlPlugin</module>
-
         <module>firestorePlugin</module>
-
         <module>redshiftPlugin</module>
-
         <module>amazons3Plugin</module>
-
         <module>googleSheetsPlugin</module>
-
         <module>graphqlPlugin</module>
-
         <module>snowflakePlugin</module>
-
         <module>arangoDBPlugin</module>
-
         <module>jsPlugin</module>
-
         <module>saasPlugin</module>
-
         <module>smtpPlugin</module>
-
         <module>openAiPlugin</module>
-
         <module>anthropicPlugin</module>
-
         <module>googleAiPlugin</module>
         <module>appsmithAiPlugin</module>
-
         <module>awsLambdaPlugin</module>
-
         <module>databricksPlugin</module>
-
     </modules>
 
     <properties>
-
         <jjwt.version>0.11.5</jjwt.version>
-
     </properties>
 
     <dependencies>
 
         <dependency>
-
             <groupId>org.pf4j</groupId>
-
             <artifactId>pf4j-spring</artifactId>
-
             <version>0.8.0</version>
-
             <scope>provided</scope>
-
             <exclusions>
-
                 <exclusion>
-
                     <groupId>org.slf4j</groupId>
-
                     <artifactId>slf4j-reload4j</artifactId>
-
                 </exclusion>
-
             </exclusions>
-
         </dependency>
 
         <dependency>
-
             <groupId>org.pf4j</groupId>
-
             <artifactId>pf4j</artifactId>
-
             <version>${org.pf4j.version}</version>
-
         </dependency>
 
         <dependency>
-
             <groupId>com.appsmith</groupId>
-
             <artifactId>interfaces</artifactId>
-
             <version>1.0-SNAPSHOT</version>
-
             <scope>provided</scope>
-
         </dependency>
 
         <dependency>
-
             <groupId>org.projectlombok</groupId>
-
             <artifactId>lombok</artifactId>
-
             <scope>provided</scope>
-
         </dependency>
 
         <!-- Test Dependencies -->
@@ -142,133 +85,86 @@
         <!-- Actual Junit5 implementation. Will transitively include junit-jupiter-api -->
 
         <dependency>
-
             <groupId>org.junit.jupiter</groupId>
-
             <artifactId>junit-jupiter-engine</artifactId>
-
             <scope>test</scope>
-
         </dependency>
 
         <dependency>
-
             <groupId>org.junit.platform</groupId>
-
             <artifactId>junit-platform-suite-engine</artifactId>
-
             <scope>test</scope>
-
         </dependency>
 
         <!-- For junit5 parameterised test support -->
 
         <dependency>
-
             <groupId>org.junit.jupiter</groupId>
-
             <artifactId>junit-jupiter-params</artifactId>
-
             <scope>test</scope>
+        </dependency>
 
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>test</scope>
         </dependency>
 
         <!-- Only required to run junit5 test from IDE -->
 
         <dependency>
-
             <groupId>org.junit.platform</groupId>
-
             <artifactId>junit-platform-launcher</artifactId>
-
             <scope>test</scope>
-
         </dependency>
 
         <dependency>
-
             <groupId>io.projectreactor</groupId>
-
             <artifactId>reactor-test</artifactId>
-
             <version>${reactor-test.version}</version>
-
             <scope>test</scope>
-
         </dependency>
 
         <dependency>
-
             <groupId>org.mockito</groupId>
-
             <artifactId>mockito-core</artifactId>
-
             <version>${mockito.version}</version>
-
             <scope>test</scope>
-
         </dependency>
 
         <dependency>
-
             <groupId>org.mockito</groupId>
-
             <artifactId>mockito-inline</artifactId>
-
             <version>${mockito.version}</version>
-
         </dependency>
 
         <!-- https://mvnrepository.com/artifact/com.squareup.okhttp3/mockwebserver3 -->
-
         <dependency>
-
             <groupId>com.squareup.okhttp3</groupId>
-
             <artifactId>mockwebserver3</artifactId>
-
             <version>${mockwebserver.version}</version>
-
             <scope>test</scope>
-
         </dependency>
 
         <!-- We need this dependency only to ensure TestContainers work with JUnit5 -->
-
         <dependency>
-
             <groupId>io.quarkus</groupId>
-
             <artifactId>quarkus-junit4-mock</artifactId>
-
             <version>2.14.2.Final</version>
-
             <scope>test</scope>
-
         </dependency>
 
         <dependency>
-
             <groupId>org.testcontainers</groupId>
-
             <artifactId>junit-jupiter</artifactId>
-
             <version>${testcontainers.version}</version>
-
             <scope>test</scope>
-
             <exclusions>
-
                 <exclusion>
-
                     <groupId>junit</groupId>
-
                     <artifactId>junit</artifactId>
-
                 </exclusion>
-
             </exclusions>
-
         </dependency>
 
     </dependencies>

app/server/appsmith-plugins/restApiPlugin/src/test/java/com/external/plugins/RestApiPluginTest.java

@@ -66,6 +66,7 @@ import static com.appsmith.external.helpers.restApiUtils.helpers.HintMessageUtil
 import static com.appsmith.external.helpers.restApiUtils.helpers.HintMessageUtils.DUPLICATE_ATTRIBUTE_LOCATION.ACTION_CONFIG_ONLY;
 import static com.appsmith.external.helpers.restApiUtils.helpers.HintMessageUtils.DUPLICATE_ATTRIBUTE_LOCATION.DATASOURCE_AND_ACTION_CONFIG;
 import static com.appsmith.external.helpers.restApiUtils.helpers.HintMessageUtils.DUPLICATE_ATTRIBUTE_LOCATION.DATASOURCE_CONFIG_ONLY;
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertIterableEquals;
@@ -1912,9 +1913,8 @@ public class RestApiPluginTest {
         StepVerifier.create(resultMono)
                 .assertNext(result -> {
                     assertFalse(result.getIsExecutionSuccess());
-                    assertTrue(result.getPluginErrorDetails()
+                    assertThat(result.getPluginErrorDetails().getDownstreamErrorMessage())
-                            .getDownstreamErrorMessage()
+                            .endsWith("Host not allowed.");
-                            .contains("Host not allowed."));
                 })
                 .verifyComplete();
     }