Endpoint user/challenger/recover

[avivash]

Summary

This PR fixes/implements the following bugs/features

• [x] user/challenge/recover endpoint to return a challenge directly from the API rather than sending an email to the user that has the challenge appended to the dashboard link

We need an endpoint that returns a challenge directly so the rs-email-service can call /v2/api/user/did/{Username}/{Challenge} on behalf of user to recover their account.

Test plan (required)

We will deploy this branch to staging to allow for easier testing before it's merged

Create a new user and call /v2/api/user/challenge/recover/{Username} with a valid UCAN as the bearer token, expect a challenge to be returned

After Merge

• [ ] Does this change invalidate any docs or tutorials? If so ensure the changes needed are either made or recorded
• [x] Does this change require a release to be made? Is so please create and deploy the release