Add user-owned IM channel connections

backend/app/gateway/auth_middleware.py

@@ -27,6 +27,7 @@ _PUBLIC_PATH_PREFIXES: tuple[str, ...] = (
     "/docs",
     "/redoc",
     "/openapi.json",
+    "/api/channels/webhooks/",
 )
 
 # Exact auth paths that are public (login/register/status check).
@@ -38,6 +39,8 @@ _PUBLIC_EXACT_PATHS: frozenset[str] = frozenset(
         "/api/v1/auth/logout",
         "/api/v1/auth/setup-status",
         "/api/v1/auth/initialize",
+        "/api/channels/slack/callback",
+        "/api/channels/discord/callback",
     }
 )