Remove NotificationHistory.template relationship

Relationship attribute is not used by the application code, so we
can remove it without replacing it with a TemplateHistory one.

This also updates the foreign key constraint to refer to the composite
primary key for the TemplateHistory records.

app/models.py

@@ -1181,8 +1181,7 @@ class NotificationHistory(db.Model, HistoryModel):
     job_row_number = db.Column(db.Integer, nullable=True)
     service_id = db.Column(UUID(as_uuid=True), db.ForeignKey('services.id'), index=True, unique=False)
     service = db.relationship('Service')
-    template_id = db.Column(UUID(as_uuid=True), db.ForeignKey('templates.id'), index=True, unique=False)
-    template = db.relationship('Template')
+    template_id = db.Column(UUID(as_uuid=True), index=True, unique=False)
     template_version = db.Column(db.Integer, nullable=False)
     api_key_id = db.Column(UUID(as_uuid=True), db.ForeignKey('api_keys.id'), index=True, unique=False)
     api_key = db.relationship('ApiKey')
@@ -1212,6 +1211,14 @@ class NotificationHistory(db.Model, HistoryModel):
     created_by = db.relationship('User')
     created_by_id = db.Column(UUID(as_uuid=True), db.ForeignKey('users.id'), nullable=True)
 
+    __table_args__ = (
+        db.ForeignKeyConstraint(
+            ['template_id', 'template_version'],
+            ['templates_history.id', 'templates_history.version'],
+        ),
+        {}
+    )
+
     @classmethod
     def from_original(cls, notification):
         history = super().from_original(notification)

tests/app/conftest.py

@@ -679,7 +679,7 @@ def sample_notification_history(
     notification_history = NotificationHistory(
         id=uuid.uuid4(),
         service=sample_template.service,
-        template=sample_template,
+        template_id=sample_template.id,
         template_version=sample_template.version,
         status=status,
         created_at=created_at,

tests/app/dao/test_provider_statistics_dao.py

@@ -73,7 +73,7 @@ def noti_hist(notify_db, template, status='delivered', billable_units=None, key_
     notification_history = NotificationHistory(
         id=uuid.uuid4(),
         service=template.service,
-        template=template,
+        template_id=template.id,
         template_version=template.version,
         status=status,
         created_at=datetime.utcnow(),