fix: adds missing DatabaseRegex field when creating FederatedDataSource

[marcosuma]

Description

Please include a summary of the fix/feature/change, including any relevant motivation and context.

Link to any related issue(s): https://jira.mongodb.org/browse/HELP-49694

Testing

This .tf extract:

[.....]
resource "mongodbatlas_federated_database_instance" "test" {
  project_id = var.project_id
  name       = var.name
  cloud_provider_config {
    aws {
      role_id        = mongodbatlas_cloud_provider_access_authorization.auth_role.role_id
      test_s3_bucket = var.test_s3_bucket
    }
  }
  storage_databases {
    name = "test_storage_databases"
    collections {
      name = "test_collections"
      data_sources {
        collection = var.collection 
        database_regex =  ".TestDB"
        store_name = var.atlas_cluster_name
        urls = []
      }
    }
  }

[.....]

was not working before, it was returning an error like:

Error: error creating MongoDB Atlas Federated Database Instace: https://cloud.mongodb.com/api/atlas/v2/groups/603f66d365f0154b5b1754ac/dataFederation POST: HTTP 400 Bad Request (Error code: "DATA_FEDERATION_STORAGE_CONFIG_INVALID") Detail: Data Federation storage config invalid. Reason: Bad Request. Params: [Federated Database Instance storage config invalid (errors: [[database 'VirtualDatabase0': collection 'test1': dataSource 0: either database or databaseRegex must be specified unless a wildcard database name is in use]]).]

Now it succeeds.

While investigating customer's issue, I found out that the field DatabaseRegex was being missed when creating a new..DataSource. This seems like a bug when creating the method

Type of change:

• Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
• New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR.
• Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR.
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the contribution guidelines
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code
• If changes include deprecations or removals, I defined an isolated PR with a relevant title as it will be used in the auto-generated changelog.

Further comments