allow service redirect uri to come from config

for external services

- ensure Spawner.oauth_client_id is always defined, not just for running Spawners

jupyterhub/app.py

@@ -1197,13 +1197,15 @@ class JupyterHub(Application):
                 )
                 self.db.add(server)
 
+            else:
+                service.orm.server = None
+
+            if service.oauth_available:
                 client_store.add_client(
                     client_id=service.oauth_client_id,
                     client_secret=service.api_token,
-                    redirect_uri=host + url_path_join(service.prefix, 'oauth_callback'),
+                    redirect_uri=service.oauth_redirect_uri,
                 )
-            else:
-                service.orm.server = None
 
             self._service_map[name] = service
 

jupyterhub/services/service.py

@@ -232,6 +232,28 @@ class Service(LoggingConfigurable):
     def _default_client_id(self):
         return 'service-%s' % self.name
 
+    oauth_redirect_uri = Unicode(
+        help="""OAuth redirect URI for this service.
+
+        You shouldn't generally need to change this.
+        Default: `/services/:name/oauth_callback`
+        """
+    ).tag(input=True)
+    @default('oauth_redirect_uri')
+    def _default_redirect_uri(self):
+        if self.server is None:
+            return ''
+        print(self.domain, self.host, self.server)
+        return self.host + url_path_join(self.prefix, 'oauth_callback')
+
+    @property
+    def oauth_available(self):
+        """Is OAuth available for this client?
+
+        Returns True if a server is defined or oauth_redirect_uri is specified manually
+        """
+        return bool(self.server is not None or self.oauth_redirect_uri)
+
     @property
     def server(self):
         if self.orm.server:

jupyterhub/user.py

@@ -203,6 +203,11 @@ class User:
             orm_spawner.state = self.state
             self.state = None
 
+        # use fully quoted name for client_id because it will be used in cookie-name
+        # self.escaped_name may contain @ which is legal in URLs but not cookie keys
+        client_id = 'user-%s' % quote(self.name)
+        if name:
+            client_id = '%s-%s' % (client_id, quote(name))
         spawn_kwargs = dict(
             user=self,
             orm_spawner=orm_spawner,
@@ -211,6 +216,7 @@ class User:
             config=self.settings.get('config'),
             proxy_spec=url_path_join(self.proxy_spec, name, '/'),
             db=self.db,
+            oauth_client_id=client_id,
         )
         # update with kwargs. Mainly for testing.
         spawn_kwargs.update(kwargs)
@@ -355,12 +361,7 @@ class User:
         # create API and OAuth tokens
         spawner.api_token = api_token
         spawner.admin_access = self.settings.get('admin_access', False)
-        # use fully quoted name for client_id because it will be used in cookie-name
-        # self.escaped_name may contain @ which is legal in URLs but not cookie keys
-        client_id = 'user-%s' % quote(self.name)
-        if server_name:
-            client_id = '%s-%s' % (client_id, quote(server_name))
-        spawner.oauth_client_id = client_id
+        client_id = spawner.oauth_client_id
         oauth_provider = self.settings.get('oauth_provider')
         if oauth_provider:
             client_store = oauth_provider.client_authenticator.client_store