Add Validity Check button to the vulnerability finding MR Security modal

Proposal

Add a way for a user to re-check the validity of an individual token in the merge request security widget modal and the vulnerability modal on the security tab of the pipeline.

Link to Designs 🎨

_{Note: As of April 4th, these designs are still a work in progress.}

Implementation Plan

• Add the button or the text on the Vulnerability Modal
• Implement a Loading state on the Front End that shows users the token's validity is being re-checked.
• Create an API that triggers the UpdateTokenStatusWorker
• Add tests