Extract EE specific files/lines for app/models/concerns (platform)

We have the following files containing EE specific code. We should move them to ee/

• app/models/concerns/reactive_caching.rb
• app/models/concerns/sha_attribute.rb

Need to figure out app/models/concerns/reactive_caching.rb and app/models/concerns/sha_attribute.rb might not be so straightforward to do.