refactor: reorganize User and OAuth model definitions for clarity and consistency

app/models.py

@@ -1,12 +1,26 @@
-from flask_login import UserMixin
-from . import db
 from flask_dance.consumer.storage.sqla import OAuthConsumerMixin
+from flask_login import UserMixin
+
+from .extensions import db
+
 
 class User(UserMixin, db.Model):
-    id = db.Column(db.Integer, primary_key=True)
+    email = db.Column(db.String(120), unique=True, nullable=False)
     name = db.Column(db.String(100), nullable=False)
-    email = db.Column(db.String(100), unique=True, nullable=False)
+    id = db.Column(db.Integer, primary_key=True)
+
 
 class OAuth(OAuthConsumerMixin, db.Model):
-    user_id = db.Column(db.Integer, db.ForeignKey(User.id))
-    user = db.relationship(User)
+    __table_args__ = (
+        db.UniqueConstraint(
+            "provider", "provider_user_id", name="uq_oauth_provider_user"
+        ),
+    )
+
+    user_id = db.Column(db.Integer, db.ForeignKey(User.id), nullable=False)
+    provider_user_id = db.Column(db.String(256), nullable=False)
+
+    user = db.relationship(
+        User,
+        backref=db.backref("oauth_accounts", cascade="all, delete-orphan"),
+    )