Add support for application settings

[glensc]

Theres /application/settings entrypoint to change Application Settings:

• https://docs.gitlab.com/ee/api/settings.html#change-application-settings

[glensc]

I don't have an actual need for this, but having this present allows to configure most of the gitlab with infrastructure as code approach, mostly for on-premise installations.

otoh, for on-premise installations some of the settings can be controlled via ominbus configuration, but seems the settings configurable via this API are not configurable via omnibus config, see the gitlab.rb.template for the list.

[gdubicki]

This feature is already nicely implemented in the „gitlab-configuration-as-code” project and mostly because of that I proposed Roche/gitlab-configuration-as-code#9 . We should get back to discussing it.

[glensc]

oh, I really like the !include and !env syntax:

• https://github.com/Roche/gitlab-configuration-as-code/blob/1224a19f01bb4268efa9a0384f6391af17e8b8bb/examples/modularized/gitlab.yml

[gdubicki]

Unfortunately Roche/gitlab-configuration-as-code#9 has stalled so we are open to PRs with this feature.

The API is really simple here - https://docs.gitlab.com/ee/api/settings.html - so it should be pretty easy.

I propose implementing it as a new config section looking like this:

application:
  settings:
    signup_enabled" : false

(Then we can easily add support for https://docs.gitlab.com/ee/api/appearance.html later on.)

[TimKnight-DWP]

We'll likely pick this up @gdubicki as we specifically want to configure 2FA settings through Application Settings config, and probably a lot more too

[gdubicki]

It has finally been implemented and release in v3.10.0 a moment ago. Thanks again, @TimKnight-DWP! 😊