rename web_server to api (#29)

* add front end code

* change licence

* rename web_server to API

* change name to web_server

api/errors/error_services.py

@@ -0,0 +1,13 @@
+from web_server.errors import RagFlowError
+
+__all__ = ['ServicesError', 'ServiceNotSupported', 'ZooKeeperNotConfigured',
+           'MissingZooKeeperUsernameOrPassword', 'ZooKeeperBackendError']
+
+
+class ServicesError(RagFlowError):
+    message = 'Unknown services error'
+
+
+class ServiceNotSupported(ServicesError):
+    message = 'The service {service_name} is not supported'
+