Make the PIN as hidden by default

[lucca65]

What we have
Today the default of the pin is to be shown, the user can toggle this to change to hidden

Proposal
Default the value to hidden

Why
To improve privacy

How
N/A

Additional context
Discovered during our Full Team session

[henriquecbuss]

Maybe we could also remember the choice of the user. So if they choose to show it, it should be shown the next times their PIN is requested, and the same if they choose to hide it

[lucca65]

nice! this would be nice! If possible, can we have a full list of preferences? I'm thinking to persist some of them in our backend on cambiatus/backend#172

I'm thinking some stuff like languages, that can affect the language of the emails

[henriquecbuss]

Can't think of much else... Other than the language, maybe the timezone could be useful for sending emails at appropriate times? Not sure...

I think the PIN preference could be stored only in localStorage, no? The only other thing I can think of is search words, but idk how useful that would be on the backend