[Applicant availability] Request availability by form
This is part of #12 (closed) and has to be implemented after #55 (closed)
As a member of the crewing team I want to request availabilty from applicants by giving them access to an availabilty form.
AC:
- The mail that is sent to the applicant now contains a link to a form instead of sending the availabilty as a payload in the email
- The link in the email is not guessable (containse a cryptographically save random uid)
- New availability form is created in public client
- Form submission is persistent
OOS:
- For now it is fine to save the "request" object that holds the "token" and other data on the public client no need for additional safety measures for now
- Dynamic "request data" endpoint and dynamic form generation in public client is not needed yet. We do that when we take our next steps