make sure original_transaction_id is unique

app/models.py

@@ -940,7 +940,8 @@ class AppleSubscription(db.Model, ModelMixin):
 
     expires_date = db.Column(ArrowType, nullable=False)
 
-    original_transaction_id = db.Column(db.String(256), nullable=False)
+    # to avoid using "Restore Purchase" on another account
+    original_transaction_id = db.Column(db.String(256), nullable=False, unique=True)
     receipt_data = db.Column(db.Text(), nullable=False)
 
     plan = db.Column(db.Enum(PlanEnum), nullable=False)

migrations/versions/2020_041923_bd05eac83f5f_.py

@@ -0,0 +1,29 @@
+"""empty message
+
+Revision ID: bd05eac83f5f
+Revises: dd911f880b75
+Create Date: 2020-04-19 23:12:26.675833
+
+"""
+import sqlalchemy_utils
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = 'bd05eac83f5f'
+down_revision = 'dd911f880b75'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_unique_constraint(None, 'apple_subscription', ['original_transaction_id'])
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_constraint(None, 'apple_subscription', type_='unique')
+    # ### end Alembic commands ###