How to deal a module included by a specified class like ActiveRecord::Base?

I write a concern module that supposes to be included by ActiveRecord::Base's subclass.

like following,

module A
  extend ActiveSupport::Concern
  included do
    has_many :hoge
  end

  def bar
    save
  end
end

In such a case, module A supposes to have ActiveRecord::Base methods.
But, in the current RBS, developers must write all ActiveRecord::Base method signatures by themselves.
Because module cannot inherit class and class cannot be included (extended).

I want a helper syntax to include method signatures of other classes whether are not modules or interfaces.

For example:

module A
  included_by ActiveRecord::Base # define method signatures with ActiveRecord::Base type
end

Start with the proposed RBS syntax for module A and the ActiveRecord::Base example in the issue. Determine how signatures from a specified class should be exposed to an included module, including the interaction with ActiveSupport::Concern. Done means the behavior and syntax are defined well enough to support this use case without requiring developers to duplicate ActiveRecord::Base signatures.