Fix destroy_all for has_many through: associations that points to a CPK model

[nvasilevski]

This PR fixes destroy_all behavior for a has_many through: association that points to a model with composite primary key however the association itself uses just id column to build the reference

Since primary_key: :id in association definition means " use the id column as primary/foreign key Rails should avoid accessing values for the column using public_send as it ends up calling the id method which in Rails has special meaning - the identifier or in other words "values behind the primary key columns" which in composite primary key context is not the same as id column. Instead we are using _read_attribute which directly fetches the value of the id column.