Add refresh_token option to backend's OAuth2TokenRequest

backend/src/routes/oauth/models.py

@@ -3,7 +3,8 @@ from typing import Optional
 
 class OAuth2TokenRequest(BaseModel):
     client_id: str
-    code: str
+    code: Optional[str]
+    refresh_token: Optional[str]
     grant_type: str
     redirect_uri: str
     code_verifier: Optional[str]