Show last used date for service tokens and PATs

[rohan-chaturvedi]

Is your feature request related to a problem?

When multiple tokens are created, particularly tokens with no expiry, its impossible to know which tokens are actually in use.

Describe the solution you'd like

• Add a last_used_at field to the Service Token model and update this value when it is used either by the CLI / SDK / API
• Show the "last used" date beside each token in App > Service Tokens. This is a timestamp for the last time the token was used to perform a CRUD action

This could be merged with #114 as some of the model and schema changes will overlap

[nishaaannnt]

Hello, @rohan-chaturvedi , we would like to work on this issue under Fosshack 2024. Me and my teammate @viku3150 are well versed with the tech stack and the codebase and hence would like to take this forward. Please assign us for the same. Thank you.