Support multiple tokens per user

[mefellows]

Currently, users are allowed to have only a single token.

This has a number of limitations:

1. Users may want to use tokens for different use cases. Re-using the same token in multiple places increases the security surface area and maintenance burden during rotation.
2. The API is not very RESTful, making it difficult for tools like Terraform to manage them. For example, only the current user can access a token's value or regenerate it - so terraform can't manage tokens on behalf of other users.

This feature is to allow multiple API Tokens per user (including System Users), with the ability to add a description for each token, and the usual CRUD capabilities.

[mefellows]

/jira ticket

[github-actions]

👋 Thanks, Jira [PACT-531] ticket created.