Add required field checks for postgres resource IDs

Changes the postgres resource ID fields (project_id, branch_id, endpoint_id)
from optional to required, matching the API's behavior. Previously these fields
were marked as omitempty but the API requires them for resource creation.

Changes:
- Mark project_id, branch_id, endpoint_id, and parent fields as required in bundle config
- Remove manual validation from direct deployment code (now handled by config validation)
- Update generated required_fields.go and JSON schema
- Add validation in test server to return 400 errors matching real API behavior
- Update acceptance test outputs to reflect new warning messages and error responses

The test server now properly validates required ID fields and returns the same
error message as the real API: "Field 'X' is required, expected non-default value (not \"\")!"

All acceptance tests pass both locally and against real AWS workspace.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: pietern

.databricks/databricks

@@ -1,5 +1,14 @@
+Warning: required field "branch_id" is not set
+  at resources.postgres_branches.main
+  in databricks.yml:21:7
+
 Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-branch-no-id-[UNIQUE_NAME]/default/files...
 Deploying resources...
-Error: cannot create resources.postgres_branches.main: branch_id must be specified
+Error: cannot create resources.postgres_branches.main: Field 'branch_id' is required, expected non-default value (not "")! (400 INVALID_PARAMETER_VALUE)
+
+Endpoint: POST [DATABRICKS_URL]/api/2.0/postgres/projects/test-pg-proj-[UNIQUE_NAME]/branches
+HTTP Status: 400 Bad Request
+API error_code: INVALID_PARAMETER_VALUE
+API message: Field 'branch_id' is required, expected non-default value (not "")!
 
 Updating deployment state...

acceptance/bundle/resources/postgres_branches/without_branch_id/out.deploy.direct.txt

@@ -1,3 +1,7 @@
+Warning: required field "branch_id" is not set
+  at resources.postgres_branches.main
+  in databricks.yml:21:7
+
 Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-branch-no-id-[UNIQUE_NAME]/default/files...
 Error: exit status 1
 

acceptance/bundle/resources/postgres_branches/without_branch_id/out.deploy.terraform.txt

@@ -1,9 +1,13 @@
 
 >>> [CLI] bundle validate
+Warning: required field "branch_id" is not set
+  at resources.postgres_branches.main
+  in databricks.yml:21:7
+
 Name: deploy-postgres-branch-no-id-[UNIQUE_NAME]
 Target: default
 Workspace:
   User: [USERNAME]
   Path: /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-branch-no-id-[UNIQUE_NAME]/default
 
-Validation OK!
+Found 1 warning

acceptance/bundle/resources/postgres_branches/without_branch_id/output.txt

@@ -1,5 +1,14 @@
+Warning: required field "endpoint_id" is not set
+  at resources.postgres_endpoints.primary
+  in databricks.yml:27:7
+
 Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-endpoint-no-id-[UNIQUE_NAME]/default/files...
 Deploying resources...
-Error: cannot create resources.postgres_endpoints.primary: endpoint_id must be specified
+Error: cannot create resources.postgres_endpoints.primary: Field 'endpoint_id' is required, expected non-default value (not "")! (400 INVALID_PARAMETER_VALUE)
+
+Endpoint: POST [DATABRICKS_URL]/api/2.0/postgres/projects/test-pg-proj-[UNIQUE_NAME]/branches/main/endpoints
+HTTP Status: 400 Bad Request
+API error_code: INVALID_PARAMETER_VALUE
+API message: Field 'endpoint_id' is required, expected non-default value (not "")!
 
 Updating deployment state...

acceptance/bundle/resources/postgres_endpoints/without_endpoint_id/out.deploy.direct.txt

@@ -1,3 +1,7 @@
+Warning: required field "endpoint_id" is not set
+  at resources.postgres_endpoints.primary
+  in databricks.yml:27:7
+
 Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-endpoint-no-id-[UNIQUE_NAME]/default/files...
 Error: exit status 1
 

acceptance/bundle/resources/postgres_endpoints/without_endpoint_id/out.deploy.terraform.txt

@@ -1,9 +1,13 @@
 
 >>> [CLI] bundle validate
+Warning: required field "endpoint_id" is not set
+  at resources.postgres_endpoints.primary
+  in databricks.yml:27:7
+
 Name: deploy-postgres-endpoint-no-id-[UNIQUE_NAME]
 Target: default
 Workspace:
   User: [USERNAME]
   Path: /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-endpoint-no-id-[UNIQUE_NAME]/default
 
-Validation OK!
+Found 1 warning

acceptance/bundle/resources/postgres_endpoints/without_endpoint_id/output.txt

@@ -1,5 +1,14 @@
+Warning: required field "project_id" is not set
+  at resources.postgres_projects.my_project
+  in databricks.yml:10:7
+
 Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-no-id-[UNIQUE_NAME]/default/files...
 Deploying resources...
-Error: cannot create resources.postgres_projects.my_project: project_id must be specified
+Error: cannot create resources.postgres_projects.my_project: Field 'project_id' is required, expected non-default value (not "")! (400 INVALID_PARAMETER_VALUE)
+
+Endpoint: POST [DATABRICKS_URL]/api/2.0/postgres/projects
+HTTP Status: 400 Bad Request
+API error_code: INVALID_PARAMETER_VALUE
+API message: Field 'project_id' is required, expected non-default value (not "")!
 
 Updating deployment state...

acceptance/bundle/resources/postgres_projects/without_project_id/out.deploy.direct.txt

@@ -1,3 +1,7 @@
+Warning: required field "project_id" is not set
+  at resources.postgres_projects.my_project
+  in databricks.yml:10:7
+
 Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-no-id-[UNIQUE_NAME]/default/files...
 Error: exit status 1
 

acceptance/bundle/resources/postgres_projects/without_project_id/out.deploy.terraform.txt

@@ -1,9 +1,13 @@
 
 >>> [CLI] bundle validate
+Warning: required field "project_id" is not set
+  at resources.postgres_projects.my_project
+  in databricks.yml:10:7
+
 Name: deploy-postgres-no-id-[UNIQUE_NAME]
 Target: default
 Workspace:
   User: [USERNAME]
   Path: /Workspace/Users/[USERNAME]/.bundle/deploy-postgres-no-id-[UNIQUE_NAME]/default
 
-Validation OK!
+Found 1 warning