Add documentation for supporting S3 with ACLs disabled and GCS unifor…

…m bucket-level access

Closes #2634, Closes #2664, Closes #2666, Closes #2667, Closes #2709

README.md

@@ -769,6 +769,10 @@ CarrierWave.configure do |config|
   config.fog_directory  = 'name_of_bucket'                                      # required
   config.fog_public     = false                                                 # optional, defaults to true
   config.fog_attributes = { cache_control: "public, max-age=#{365.days.to_i}" } # optional, defaults to {}
+  # Use this if you have AWS S3 ACLs disabled.
+  # config.fog_attributes = { 'x-amz-acl' => 'bucket-owner-full-control' }
+  # Use this if you have Google Cloud Storage uniform bucket-level access enabled.
+  # config.fog_attributes = { uniform: true }
   # For an application which utilizes multiple servers but does not need caches persisted across requests,
   # uncomment the line :file instead of the default :storage.  Otherwise, it will use AWS as the temp cache store.
   # config.cache_storage = :file