Content API - only save if there are actual changes

For every "update" action on the Content API it should check if there are actual differences between the latest saved version and the data being updated and skip if the data is equal.

- Do not trigger the loading mechanism that demands server resources
- Save DB resources by not inserting unnecessary data

Locate the Content API's update action and trace how it loads the latest saved version and persists incoming data. Compare those values before the loading and database-saving steps; done means equal updates perform neither operation, while changed data still updates normally.

Written by the indexing model from the issue text.