Add exceptions for metadata modules (#6070)

Class exception for each metadata module + handler to map on graphql
error

TODO left :
- find a way to call handler on auto-resolvers nestjs query (probably
interceptors)
- discuss what should be done for pre-hooks errors
- discuss what should be done for Unauthorized exception

packages/twenty-server/src/engine/metadata-modules/data-source/data-source.exception.ts

@@ -0,0 +1,11 @@
+import { CustomException } from 'src/utils/custom-exception';
+
+export class DataSourceException extends CustomException {
+  constructor(message: string, code: DataSourceExceptionCode) {
+    super(message, code);
+  }
+}
+
+export enum DataSourceExceptionCode {
+  DATA_SOURCE_NOT_FOUND = 'DATA_SOURCE_NOT_FOUND',
+}