auto lock and secret service should be mutually exclusive

[paolostivanin]

I recently upgraded from 2.4.x to 3.1.x, read about the new Secret service integration feature, left it on, and was surprised to see I got:

1. No password at startup ...
2. ... but got asked for a password after an Auto lock (because I was migrated from a 2.4 with Auto Lock options on) ...
3. ... which was defeated by simply restarting the app!

→ What's the point of enabling options Auto lock on system lock and Auto lock when inactive for ... if all you have to do to unlock the app is to restart it?!

Said differently, it feels like options Auto lock vs. Secret service integration are mutually exclusive:

1. The app should GTK-disable the two Auto lock options ("grey them out") when the Secret service feature is enabled. Rationale: the lock is meaningless security-wise if you have Secret service integration, and only adds bogus friction.
2. The app should GTK-disable Secret service integration if one of the two Auto lock options are enabled. Rationale: if you use Auto lock, then you want control over when to lock/unlock, and you want to be prompted at startup.

Does that make sense? Am I missing something?

Originally posted by @ronjouch in #264 (comment)