Rate limiting on pass reset

[tkaraivanov]

Users can request a new email to be sent no less than X seconds after the last request.
Initially X = 0. Submitting the a request increases it by 60 for 1 hour.
So the second request would be after 2 minutes, third after 3, etc. But the time increase expires in 1 hour.

We need a timer on the pass reset frontend showing how long until they can request again. However, this needs to be validated on the backend as well.