chore(docs): add field repository_update_events

What does this MR do?

It adds the field reposistory_update_events to the json response and as input parameter for adding a new system hook via api.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides