Add user OAUTH application authorisation audit event

Audit need

Currently, when a user adds/removes an OAuth application, no audit event is generated. This event is important for security team to monitor the OAuth applications authorised by user on a specific gitlab instance.

Proposal

When user successfully authorise an OAuth application, then add an event saying User authorised an OAuth application along with the application id. Details that could be added to the event:

• IP address
• Author
• Application ID
• user-id

We have recently added an MR to log this event in the production_json.log file.

Streaming-only event or normal event?

It could be a normal event as the volume won't be too much.