feat: support filtering on composite type columns

[mattbretl]

Closes #114

TODO:

• [ ] Make this opt-in via plugin option
• [ ] Extend tests to include nested composite types

[jcgsville]

Just tested this with cases that I believe do not work:

• Computed column that returns a composite type
• Composite type that has a domain-constrained property
• Domain that is a composite type with a check (though this one doesn't work in postgraphile currently)

Happy to provide minimal repros if that would help

[mattbretl]

@jcgsville Yes, minimal repros would be a huge help. :pray:

Feel free to open a new issue for this.

[jcgsville]

Finally got around to providing repros, and I realized that I must have been mistaken for the first and second cases. Apologies for the confusion.

And I expect the third case will be solved by https://github.com/graphile/graphile-engine/pull/615.

I'd love to see this integrated in the plugin, though. In the meantime, we are using this branch in our project 😬

[EyMaddis]

I think this might run into problems with composite types: https://github.com/graphile-contrib/postgraphile-plugin-connection-filter/issues/124

[mattbretl]

Closing this PR, since composite types are now supported in 2.0.0.

@EyMaddis I've created a new issue (#126) with a reminder to add tests related to NULL.