chore: refactor crud repository methods (appsmithorg#38144)

## Description
As part of transaction support in PG, we are moving from using the jpa
methods for database operations. This PR is refactoring the code to use
custom repository class for DatasourceStorageStructureRepository from
the default CrudRepository.

## Automation

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

### 🔍 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/12310505479>
> Commit: f226809
> <a
href="https://internal.appsmith.com/app/cypress-dashboard/rundetails-65890b3c81d7400d08fa9ee5?branch=master&workflowId=12310505479&attempt=2"
target="_blank">Cypress dashboard</a>.
> Tags: `@tag.Datasource`
> Spec:
> <hr>Fri, 13 Dec 2024 07:34:38 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**
- Introduced a method to retrieve `DatasourceStorageStructure` based on
datasource and environment identifiers.
  
- **Bug Fixes**
- Simplified the structure of the
`DatasourceStorageStructureRepositoryCE` interface by removing an
outdated method.

- **Documentation**
- Added `@Repository` annotation to the
`DatasourceStorageStructureRepositoryCE` interface to indicate its role
as a Spring Data repository.

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

appsmith-server/src/main/java/com/appsmith/server/repositories/ce/CustomDatasourceStorageStructureRepositoryCE.java

@@ -1,9 +1,12 @@
 package com.appsmith.server.repositories.ce;
 
+import com.appsmith.external.models.DatasourceStorageStructure;
 import com.appsmith.external.models.DatasourceStructure;
 import reactor.core.publisher.Mono;
 
 public interface CustomDatasourceStorageStructureRepositoryCE {
 
     Mono<Integer> updateStructure(String datasourceId, String environmentId, DatasourceStructure structure);
+
+    Mono<DatasourceStorageStructure> findByDatasourceIdAndEnvironmentId(String datasourceId, String environmentId);
 }

appsmith-server/src/main/java/com/appsmith/server/repositories/ce/CustomDatasourceStorageStructureRepositoryCEImpl.java

@@ -3,6 +3,7 @@
 import com.appsmith.external.models.DatasourceStorageStructure;
 import com.appsmith.external.models.DatasourceStructure;
 import com.appsmith.server.helpers.ce.bridge.Bridge;
+import com.appsmith.server.helpers.ce.bridge.BridgeQuery;
 import com.appsmith.server.repositories.BaseAppsmithRepositoryImpl;
 import org.springframework.stereotype.Component;
 import reactor.core.publisher.Mono;
@@ -19,4 +20,13 @@ public Mono<Integer> updateStructure(String datasourceId, String environmentId,
                         .equal(DatasourceStorageStructure.Fields.environmentId, environmentId))
                 .updateFirst(Bridge.update().set(DatasourceStorageStructure.Fields.structure, structure));
     }
+
+    @Override
+    public Mono<DatasourceStorageStructure> findByDatasourceIdAndEnvironmentId(
+            String datasourceId, String environmentId) {
+        final BridgeQuery<DatasourceStorageStructure> q = Bridge.<DatasourceStorageStructure>equal(
+                        DatasourceStorageStructure.Fields.datasourceId, datasourceId)
+                .equal(DatasourceStorageStructure.Fields.environmentId, environmentId);
+        return queryBuilder().criteria(q).one();
+    }
 }

appsmith-server/src/main/java/com/appsmith/server/repositories/ce/DatasourceStorageStructureRepositoryCE.java

@@ -3,10 +3,8 @@
 import com.appsmith.external.models.DatasourceStorageStructure;
 import com.appsmith.server.repositories.BaseRepository;
 import com.appsmith.server.repositories.CustomDatasourceStorageStructureRepository;
-import reactor.core.publisher.Mono;
+import org.springframework.stereotype.Repository;
 
+@Repository
 public interface DatasourceStorageStructureRepositoryCE
-        extends BaseRepository<DatasourceStorageStructure, String>, CustomDatasourceStorageStructureRepository {
-
-    Mono<DatasourceStorageStructure> findByDatasourceIdAndEnvironmentId(String datasourceId, String environmentId);
-}
+        extends BaseRepository<DatasourceStorageStructure, String>, CustomDatasourceStorageStructureRepository {}