Add configurable option for bypass_two_factor of oauth

Problem to solve

bypass_two_factor in oauth is hard coded as false now. Some oauth method has already required two-factor, user has to do two-factor auth again....

Target audience

Software Developer or Community, if this proposal is acceptable, I can create a merge request for this also.

Further details

Proposal

What does success look like, and how can we measure that?

Add a key bypass_two_factor under config gitlab_rails['omniauth_providers'] like this:

gitlab_rails['omniauth_enabled'] = true
gitlab_rails['omniauth_allow_single_sign_on'] = ['oauth2_generic']
gitlab_rails['omniauth_block_auto_created_users'] = true
gitlab_rails['omniauth_providers'] = [
  {
    'name' => 'oauth2_generic',
    'bypass_two_factor' => true,
    'app_id' => 'gitlab',
    'app_secret' => '9zQf3mvqe8LnN9',
    'args' => {
      client_options: {
        'site' => 'http://oauth.example.com/', # including port if necessary
        'user_info_url' => '/gitlab/user'
      },
      user_response_structure: {
        #root_path: ['data', 'user'], # i.e. if attributes are returned in JsonAPI format (in a 'user' node nested under a 'data' node)
        #attributes: { nickname: 'username' } # if the nickname attribute of a user is called 'username'
      },
      # optionally, you can add the following two lines to "white label" the display name
      # of this strategy (appears in urls and Gitlab login buttons)
      # If you do this, you must also replace oauth2_generic, everywhere it appears above, with the new name.
      name: 'OAuth', # display name for this strategy
      strategy_class: "OmniAuth::Strategies::OAuth2Generic" # Devise-specific config option Gitlab uses to find renamed strategy
    }
  }
]

Links / references