Feat/improve error management in core module (#8933)

## Summary
This Pull Request introduces a custom validator for checking forbidden
words in workspaces and refines how exceptions are handled within the
workspace module.

- Introduced `ForbiddenWords` custom class validator for validating
forbidden words against specific fields in `UpdateWorkspaceInput`.
- Added `EnvironmentService` usage in `WorkspaceService` to check
default subdomains.
- New file `workspaceGraphqlApiExceptionHandler` to handle GraphQL API
exceptions with specific error mappings.
- Expanded `WorkspaceExceptionCode` with `SUBDOMAIN_ALREADY_TAKEN`.
- Added new unit tests for validating forbidden words and exception
handler behavior.

packages/twenty-server/src/engine/utils/__tests__/forbidden-words-custom-class-validator.spec.ts

@@ -0,0 +1,38 @@
+import { validate } from 'class-validator';
+
+import { ForbiddenWords } from 'src/engine/utils/custom-class-validator/ForbiddenWords';
+
+describe('ForbiddenWordsConstraint', () => {
+  test('should throw error when word is forbidden', async () => {
+    class Test {
+      @ForbiddenWords(['forbidden', 'restricted'])
+      subdomain: string;
+    }
+
+    const instance = new Test();
+
+    instance.subdomain = 'forbidden';
+
+    const errors = await validate(instance);
+
+    expect(errors.length).toBeGreaterThan(0);
+    expect(errors[0].constraints).toEqual({
+      ForbiddenWordsConstraint: 'forbidden, restricted are not allowed',
+    });
+  });
+
+  test('should pass validation word is not in the list', async () => {
+    class Test {
+      @ForbiddenWords(['forbidden', 'restricted'])
+      subdomain: string;
+    }
+
+    const instance = new Test();
+
+    instance.subdomain = 'valid';
+
+    const errors = await validate(instance);
+
+    expect(errors.length).toEqual(0);
+  });
+});