Fix where the documentation says "photos", but the example shows "posts" or "comments" by switching both to simply "posts"

Add further documentation + examples for the get, post, put and delete methods in ActionDispatch::Routing::Mapper::HttpHelpers

only returning where values for the corresponding relation, also filtering where value hash based on table name [#5234 state:resolved] [#5184 state:resolved]

Convert :primary_key in association to a string before comparing to column names, so that for example :primary_key => :another_pk works as well [#5605 state:resolved]

Refactoring: replace the mix of variables like @finder_sql, @counter_sql, etc with just a single scope hash (created on initialization of the proxy). This is now used consistently across all associations. Therefore, all you have to do to ensure finding/counting etc is done correctly is implement the scope correctly.

We saw a failing spec when running the DataMapper
ActiveModel compliance specs for dm-active_model.

  ActiveModel::Naming#model_name

relies on the Module#parents method defined in

  active_support/core_ext/module/introspection.rb

Adding the appropriate require statement of course
fixed our specs.