Bug: secrets do not apply custom Unix permissions

[paulmiro]

When deploying secrets, the resulting file always has the default 0400 permissions, even when lollypops.secrets.files.<name>.mode is set to another value (for example 0440).

It also does not throw an error when the option is set to a value that should be invalid

[pinpox]

@paulmiro You are right! The change of mode seems to have been lost on some merge, sorry. I added a WIP PR that should fix this, feel free to test and give me some feedback. I'll get around to testing later this week otherwise