[CDAPI-71]: Added specific error response for mock errors

Author: nhsd-jack-wainwright

mocks/src/pdm_mock/handler.py

@@ -178,9 +178,9 @@ def create_document() -> Response[str]:
 
     try:
         response = handle_post_request(payload)
-    except Exception:
+    except Exception as err:
         _logger.exception("Error handling PDM request")
-        raise
+        return Response(status_code=500, body=json.dumps({"error": str(err)}))
 
     return _with_default_headers(response)
 
@@ -191,8 +191,8 @@ def get_document(document_id: str) -> Response[str]:
 
     try:
         response = handle_get_request(document_id)
-    except Exception:
+    except Exception as err:
         _logger.exception("Error handling PDM request")
-        raise
+        return Response(status_code=500, body=json.dumps({"error": str(err)}))
 
     return _with_default_headers(response)