Authorization checks in server.py

This commit adds a single parameter used in the
`config.authorize_callback` that allows the user supplied method to
check if an app user is authorized to view the requested app at the
given path.

Resolves holoviz#3179

panel/io/server.py

@@ -485,7 +485,7 @@ async def get(self, *args, **kwargs):
                 token = session.token
             logger.info(LOG_SESSION_CREATED, id(session.document))
             with set_curdoc(session.document):
-                if config.authorize_callback and not config.authorize_callback(state.user_info):
+                if config.authorize_callback and not config.authorize_callback(state.user_info, self.request.path):
                     if config.auth_template:
                         with open(config.auth_template) as f:
                             template = _env.from_string(f.read())