Add support for non-embedded associations

[travisp]

Not everyone uses the "embed" functionality of ActiveModel::Serializers, and it would be nice if postgres_ext-serializers could support associations in this case (and in the meantime, print a warning or include information in the readme about this).

In theory, it shouldn't be too difficult, as it just requires a nested row_to_json (for has_one) or json_agg (for has_many) on the sub serializers query and the where clause. Much of the code for this already exists, but it's just focused on putting the embedded object in root rather than nested within other objects.

Would there be support for this extension of postgres_ext-serializers?

[danmcclain]

I'm not sure I understand exactly what you are asking for. And postgres_ext-serializers so far only includes what I've needed to build for the things I was working on at the time. Very much open to any pull request that extends the functionality to support more cases

[felixbuenemann]

I'm not sure I understand what you are proposing. Could you maybe post the expected JSON?