User enumeration possibility

We have this hard coded duration range in the password hint code:

https://github.com/dani-garcia/vaultwarden/blob/d6a3d539ed13352085ca7dfa63c49017d86c419b/src/api/core/accounts.rs#L1200-L1205

Now, the problem with this is that in my setup it is clearly visible which users exists and which do not, just based on the response time of the query.

I see a possible mitigation to this by letting the users control the range via configuration values so that users can specify ranges that closely match their otherwise usual mail sending delays.

Thank you for your attention to this matter.