has_many :through broken

[felixbuenemann]

Serializing a has_many :through relation is currently broken and results in invalid SQL due to bad column references.

postgres_ext-serializers handles these like a normal has_many relation, when instead it needs to lookup the through_reflection and join the underlying join table to be able to lookup the proper ids.

[felixbuenemann]

This likely also affects has_and_belongs_to_many, which is just a special case of has_many :through.