add option to disable form login

[kyuuk]

Fixes #730

Add an option to disable login form, this hides the username and password fields and Login button,
i also changed the Login with OIDC button css classes to make it a little better when form is disabled
which gives a for like this :

i'm not sure about the frontend part , it could probably be improved.

• Added test to validate that by default fiels are still present
• Added test to validate that fields are not present when option is true

[sissbruecker]

Reading through #730 again, I don't think the intention is to hide the login form. The goal is to automatically initiate the OIDC flow when opening the app without having to click a button on the login page.

[kyuuk]

I saw that also, but understood that it was a separate optional feature.

I’m thinking of implementing that also, but i don't want to mess too much as i'm not good with frontend.

I’ll try asking in #730 if someone can help with this part.