Add ignoring of the self-registration setting.

[skokhanovskiy]

Adds a new setting which allows to override the Redmine self_registration option and force a creation of a new account if the normal registration is disabled.

Tested on

  Redmine version                3.4.6.stable
  Ruby version                   2.3.3-p222 (2016-11-21) [x86_64-linux-gnu]
  Rails version                  4.2.8

Based on this pull request from root repository: twinslash#9

[tasogarei]

Thank you pull request.
I want to think a bit about this feature.

[skokhanovskiy]

This feature is "must have" if your redmine installation is non-public and for a corporate users only. It's usable in case when redmine's "self-registration" setting is disabled and domain restrictions specifiied by the "available domains" setting of the redmine_omniauth_google plugin. Enabling this option allows you to disable the standart redmine form for registering new users. But at the same time it
allows register users through oauth2 with manual account activation.

[skokhanovskiy]

Up.