Make transaction.meter_end required and force tz utc for all datetimes

backend/app/schemas/auth_token.py

@@ -3,6 +3,7 @@ from datetime import datetime
 from pydantic import BaseModel
 
 from app.schemas.user import Role
+from app.util.encoders import force_utc_datetime
 
 
 @dataclass
@@ -19,3 +20,6 @@ class TokenResponse(BaseModel):
     access_token: str
     refresh_token: str
     not_after: datetime
+
+    class Config:
+        json_encoders = {datetime: force_utc_datetime}