Fixed name for OAUTH_AUTO_SIGN_IN_WITH_PROVIDER

The provider list is fixed this creates issues when using the generic oauth2 provider when using a different name.
https://github.com/sameersbn/docker-gitlab/blob/c773d84f452a59a0ffd6c8374883c423c751174b/assets/runtime/functions#L703

This config will restult in an error:

  ## OmniAuth settings
  omniauth:
    # Allow login via Twitter, Google, etc. using OmniAuth providers
    enabled: true

    # Uncomment this to automatically sign in with a specific omniauth provider's without
    # showing GitLab's sign-in page (default: show the GitLab sign-in page)
    auto_sign_in_with_provider: oauth2_generic

    # Sync user's email address from the specified Omniauth provider every time the user logs
    # in (default: nil). And consequently make this field read-only.
    # sync_email_from_provider: cas3

    # CAUTION!
    # This allows users to login without having a user account first. Define the allowed providers
    # using an array, e.g. ["saml", "twitter"], or as true/false to allow all providers or none.
    # User accounts will be created automatically when authentication was successful.
    allow_single_sign_on: []

    # Locks down those users until they have been cleared by the admin (default: true).
    block_auto_created_users: true
    # Look up new users in LDAP servers. If a match is found (same uid), automatically
    # link the omniauth identity with the LDAP account. (default: false)
    auto_link_ldap_user: false

    # Allow users with existing accounts to login and auto link their account via SAML
    # login, without having to do a manual login first and manually add SAML
    # (default: false)
    auto_link_saml_user: false

    # Set different Omniauth providers as external so that all users creating accounts
    # via these providers will not be able to have access to internal projects. You
    # will need to use the full name of the provider, like `google_oauth2` for Google.
    # Refer to the examples below for the full names of the supported providers.
    # (default: [])
    external_providers: []

    ## Auth providers
    # Uncomment the following lines and fill in the data of the auth provider you want to use
    # If your favorite auth provider is not listed you can use others:
    # see https://github.com/gitlabhq/gitlab-public-wiki/wiki/Custom-omniauth-provider-configurations
    # The 'app_id' and 'app_secret' parameters are always passed as the first two
    # arguments, followed by optional 'args' which can be either a hash or an array.
    # Documentation for this is available at http://doc.gitlab.com/ce/integration/omniauth.html
    providers:
      # See omniauth-cas3 for more configuration details
      - { name: 'oauth2_generic',
          app_id: 'gitlab',
          app_secret: 'fa48e546-6a14-4c83-8403-5c4dc9cda14b',
          args: {
            client_options: {
              site: 'https://identity-o.serverhostname.be/',
              user_info_url: 'https://identity-o.serverhostname.be/auth/realms/coolrealm/protocol/openid-connect/userinfo',
              authorize_url: 'https://identity-o.serverhostname.be/auth/realms/coolrealm/protocol/openid-connect/auth',
              token_url: 'https://identity-o.serverhostname.be/auth/realms/coolrealm/protocol/openid-connect/token',
              end_session_endpoint: 'https://identity-o.serverhostname.be/auth/realms/coolrealm/protocol/openid-connect/logout',
                        },
            user_response_structure: {
            id_path: 'sub',
            attributes: {
              uid: 'sub',
              name: 'preferred_username',
              email: 'email'
              }
            },
            name: 'IdentityServer' }}

Results in following error:

Processing by SessionsController#new as HTML
Completed 500 Internal Server Error in 22ms (ActiveRecord: 1.3ms | Elasticsearch: 0.0ms | Allocations: 5544)
  
NoMethodError (undefined method `user_oauth2_generic_omniauth_authorize_path' for #<ActionDispatch::Routing::RoutesProxy:0x0000556b3e8c4890>):
  
app/controllers/sessions_controller.rb:249:in `auto_sign_in_with_provider'
app/controllers/application_controller.rb:479:in `set_current_admin'
lib/gitlab/session.rb:11:in `with_session'
app/controllers/application_controller.rb:470:in `set_session_storage'
lib/gitlab/i18n.rb:55:in `with_locale'
lib/gitlab/i18n.rb:61:in `with_user_locale'
app/controllers/application_controller.rb:464:in `set_locale'
lib/gitlab/error_tracking.rb:34:in `with_context'
app/controllers/application_controller.rb:555:in `sentry_context'
lib/gitlab/application_context.rb:46:in `block in use'
lib/gitlab/application_context.rb:46:in `use'
lib/gitlab/application_context.rb:19:in `with_context'
app/controllers/application_controller.rb:455:in `set_current_context'
lib/gitlab/request_profiler/middleware.rb:17:in `call'
lib/gitlab/middleware/go.rb:20:in `call'
lib/gitlab/etag_caching/middleware.rb:13:in `call'
lib/gitlab/middleware/multipart.rb:121:in `call'
lib/gitlab/middleware/read_only/controller.rb:53:in `call'
lib/gitlab/middleware/read_only.rb:18:in `call'
lib/gitlab/middleware/basic_health_check.rb:25:in `call'
lib/gitlab/middleware/request_context.rb:23:in `call'
config/initializers/fix_local_cache_middleware.rb:9:in `call'
lib/gitlab/metrics/requests_rack_middleware.rb:49:in `call'
lib/gitlab/middleware/release_env.rb:12:in `call'

This problem is fixed replacing the auto_sign_in_with_provider: oauth2_generic with in this case IdentityServer.

Start at assets/runtime/functions around line 703, then trace the auto_sign_in_with_provider call named in app/controllers/sessions_controller.rb:249. Reproduce the configuration with a custom provider name and verify that automatic sign-in no longer raises the undefined route error for that provider.