Hyrax::Forms::CollectionForm.model_class gets set before configuration is read

[ryanfb]

Descriptive summary

In Hyrax v5, the default for Hyrax.config.collection_model changed from '::Collection' to 'Hyrax::PcdmCollection' (https://github.com/samvera/hyrax/blob/main/lib/hyrax/configuration.rb#L898). This should be able to be overridden by setting Hyrax.config.collection_model = '::Collection' in a Hyrax initializer. Unfortunately, Hyrax::Forms::CollectionForm.model_class seems to be initialized before configuration takes place (https://github.com/samvera/hyrax/blob/main/app/forms/hyrax/forms/collection_form.rb#L19), causing a default of Hyrax::PcdmCollection to persist in Hyrax::Forms::CollectionForm.model_class when interacting with any CollectionForm.

Steps to reproduce the behavior in User Interface (UI)

1. Set Hyrax.config.collection_model = '::Collection' in e.g. config/initializers/hyrax.rb
2. Boot Hyrax app
3. Hyrax::Forms::CollectionForm.model_class should evaluate to ::Collection, but is instead Hyrax::PcdmCollection

Actual behavior (include screenshots if available)

Upgrading from 4.x to 5.x and expecting old ::Collection behavior to persist results in lots of unexpected broken behavior around Collections.

Acceptance Criteria/Expected Behavior

• Setting Hyrax.config.collection_model = '::Collection' persists to Hyrax::Forms::CollectionForm.model_class

An easy workaround would be to have an environment variable like HYRAX_COLLECTION_MODEL optionally used for the default before falling back to a hardcoded default. A clean fix would be to defer setting Hyrax::Forms::CollectionForm.model_class until after Rails configuration/initialization has taken place.