[1.5.0] Ad existing vault: point user to recovery key

[StanoRiga]

Summary

After adding a vault (no matter if new or existing), users should be actively made aware of the recovery key

Motivation

When creating a new vault, the user is actively made aware of the recovery key (and must confirm that he saved it). But if he just ads an existing vault, or if he migrates one, there's no popup. You have to remind on your own to look up the key in the vault options and save it.
As the recovery key might be relevant, there should be a note in every scenarios that adds a vault to cryptomator.

[overheadhunter]

There can be many reasons to add a vault. One of the most obvious might be that one wants to access the vault from a new device. It is very likely that one has recently dealed with the recovery key on the device the vault has been created on, originally.

I'd suggest to instead remind about the recovery key every now and then. Like the way websites ask you about confirming your 2fa settings from time to time.

This way we would include any vaults, no matter how or when they have been added or migrated. The time interval is debatable and of course there should be an options to turn off those notifications, as some people might find them annoying.

What do you think about this?