Fix invalid Content-Type header for WebP images (#26773)

config/initializers/mime_types.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
-# Be sure to restart your server when you modify this file.
-
 Mime::Type.register 'application/json', :json, %w(text/x-json application/jsonrequest application/jrd+json application/activity+json application/ld+json)
 Mime::Type.register 'text/xml',         :xml,  %w(application/xml application/atom+xml application/xrd+xml)
+
+# WebP is not defined in Rack 2.2.
+Rack::Mime::MIME_TYPES['.webp'] = 'image/webp'

spec/models/media_attachment_spec.rb

@@ -105,6 +105,9 @@ RSpec.describe MediaAttachment, paperclip_processing: true do
 
       # sets file extension
       expect(media.file_file_name).to end_with extension
+
+      # Rack::Mime (used by PublicFileServerMiddleware) recognizes file extension
+      expect(Rack::Mime.mime_type(extension, nil)).to eq content_type
     end
 
     it 'saves media attachment with correct size metadata' do