[Draft] Allow uncancel request

**Is your feature request related to a problem? Please describe.**
Mentees are asked to cancel their other requests once one of their request approved.
Sometimes the mentors is not responding and they would like to re-send the cancel requests. Currently it's not possible.

**Describe the solution you'd like**
Allow re-submit a request to mentor

**Describe alternatives you've considered**
Do it manually by the website admin

* This issue should be improved (I just put it here to not forget)

No files, tests, or entry points are named. Start by tracing the request cancellation workflow in the repository and determine how a mentee's cancelled request is stored and submitted; done means an eligible mentee can resubmit it to an unresponsive mentor without admin intervention, with the relevant workflow covered by tests.

Written by the indexing model from the issue text.