Prevent key recovery for foreign vault

[overheadhunter]

Prevent using a recovery key if a vault config file exists and the provided key didn't sign it.

This fixes #2076 and prevents people from "false positive key recoveries" that led to follow-up errors (empty vault).

[infeo]

I really love this contribution 💚 : Reduced possibility to screw up a vault, reduced support on our side and improved usability.

Speaking about useability: Can you add in the ui a label with the cross icon when the text entered in the recover text box is not a valid recovery key. Otherwise the user would ask why she cannot click on the next button.

Like the positive case

and similar to the valid-path-label in the CreateNewVaultLocationController.

[overheadhunter]

I tried but didn't succeed without adding a disproportionate amount of complexity in the fxml file, therefore I decided this issue is about preventing bad things from happening, not about explaining why a recovery key is considered invalid.

The button being disabled without explanation is not a regression, so let's not use the review to sneak in other new features. 😉

[infeo]

Well ok, worth a try. But then one step after another.