DEV: Deprecate OAuth2Authenticator and OAuth2UserInfo (#15427)

These have been superseded by ManagedAuthenticator and UserAssociatedAccount. For more information, see https://meta.discourse.org/t/106695

lib/auth/oauth2_authenticator.rb

@@ -8,6 +8,7 @@ class Auth::OAuth2Authenticator < Auth::Authenticator
 
   # only option at the moment is :trusted
   def initialize(name, opts = {})
+    Discourse.deprecate("OAuth2Authenticator is deprecated. Use `ManagedAuthenticator` and `UserAssociatedAccount` instead. For more information, see https://meta.discourse.org/t/106695", drop_from: '2.9.0', output_in_test: true)
     @name = name
     @opts = opts
   end

lib/discourse.rb

@@ -876,7 +876,7 @@ module Discourse
     digest = Digest::MD5.hexdigest(warning)
     redis_key = "deprecate-notice-#{digest}"
 
-    if !Discourse.redis.without_namespace.get(redis_key)
+    if Rails.logger && !Discourse.redis.without_namespace.get(redis_key)
       Rails.logger.warn(warning)
       begin
         Discourse.redis.without_namespace.setex(redis_key, 3600, "x")