fix schema and primary key

* version is an additional primary key so we need to indicate that
* schema no longer relies on Template model, and uses nested user

app/models.py

@@ -249,7 +249,7 @@ class TemplateHistory(db.Model):
     subject = db.Column(db.Text)
     created_by_id = db.Column(UUID(as_uuid=True), db.ForeignKey('users.id'), index=True, nullable=False)
     created_by = db.relationship('User')
-    version = db.Column(db.Integer)
+    version = db.Column(db.Integer, primary_key=True)
 
 
 MMG_PROVIDER = "mmg"

app/schemas.py

@@ -172,17 +172,11 @@ class TemplateSchema(BaseTemplateSchema):
 
 class TemplateHistorySchema(BaseSchema):
 
-    class Meta:
-        # Use the base model class that the history class is created from
-        model = models.Template
-    # We have to use a method here because the relationship field on the
-    # history object is not created.
-    created_by = fields.Method("populate_created_by", dump_only=True)
+    created_by = fields.Nested(UserSchema, only=['id', 'name', 'email_address'], dump_only=True)
     created_at = field_for(models.Template, 'created_at', format='%Y-%m-%d %H:%M:%S.%f')
 
-    def populate_created_by(self, data):
-        usr = models.User.query.filter_by(id=data.created_by_id).one()
-        return {'id': str(usr.id), 'name': usr.name, 'email_address': usr.email_address}
+    class Meta:
+        model = models.TemplateHistory
 
 
 class NotificationsStatisticsSchema(BaseSchema):

app/service/rest.py

@@ -176,7 +176,7 @@ def get_service_provider_aggregate_statistics(service_id):
 # tables. This is so product owner can pass stories as done
 @service.route('/<uuid:service_id>/history', methods=['GET'])
 def get_service_history(service_id):
-    from app.models import (Service, ApiKey, Template, Event)
+    from app.models import (Service, ApiKey, Template, TemplateHistory, Event)
     from app.schemas import (
         service_history_schema,
         api_key_history_schema,