Fix SAWarning by adding labels to the services order query
Fix SAWarning by adding labels to the services order query

When adding .pagination to the query SQLAlchemy transforms it into
a subselect and reuses the `anon_1` label for the subquery result.

Adding explicit labels to the order_by columns removes the name
conflict and the warning.

RichardKnop/digitalmarketplace-api,alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api,mtekel/digitalmarketplace-api,RichardKnop/digitalmarketplace-api,mtekel/digitalmarketplace-api,mtekel/digitalmarketplace-api,mtekel/digitalmarketplace-api,RichardKnop/digitalmarketplace-api,alphagov/digitalmarketplace-api,RichardKnop/digitalmarketplace-api