Build namespace types as object types

[jwils]

Summary

Namespace types are now built as regular ObjectType instances via new_object_type. new_namespace_type applies the namespace-specific settings (graphql_only true and resolve_fields_with nil) before yielding, so object-type factory extensions apply to namespace types without swapping constructors or maintaining a dedicated NamespaceType subclass.

Because GraphQL-only types have no backing datastore representation, HasIndices#index now rejects index definitions on any GraphQL-only type. That keeps namespace types unindexable at the shared indexing boundary instead of via a namespace-only subclass override.

The Apollo factory extension no longer needs a separate namespace hook because namespace creation now flows through its existing new_object_type extension.

Testing Performed

• bundle exec rspec elasticgraph-schema_definition/spec/unit/elastic_graph/schema_definition/factory_spec.rb
• bundle exec rspec elasticgraph-schema_definition/spec/unit/elastic_graph/schema_definition/graphql_schema/namespace_type_spec.rb elasticgraph-schema_definition/spec/unit/elastic_graph/schema_definition/graphql_schema/object_type_spec.rb
• bundle exec rspec elasticgraph-schema_definition/spec/unit/elastic_graph/schema_definition/runtime_metadata/object_types_by_name/namespace_type_spec.rb elasticgraph-schema_definition/spec/unit/elastic_graph/schema_definition/datastore_config/index_mappings/namespace_type_spec.rb
• bundle exec rspec elasticgraph-apollo/spec/unit/elastic_graph/apollo/schema_definition_spec.rb
• script/type_check
• script/lint
• git diff --check

[myronmarston]

The approach you've taken here feels pretty messy. Temporarily changing what's essentially a global variable never feels good.

Two alternate approaches I'd consider:

1. Delegation: instead of having NamespaceType subclass ObjectType, do class NamespaceType < DelegateClass(ObjectType) so that it wraps an object_type instance. Then a new_object_type override in an extension will apply to the ObjectType that gets wrapped by NamespaceType.
2. Don't use a separate type for namespace_type at all--instead, have factory.new_namespace_type use factory.new_object_type and apply namespace-specific settings (e.g. graphql_only true, resolve_fields_with nil) to it before yielding. For the index override that raises an error we could have the root index method raise an error for graphql_only types as it doesn't make sense to define an index on a graphql-only type.

I think I like the latter solution best, as namespace_type.rb doesn't really have much logic.

Thoughts?

[jwils]

Option 1 I think looked just as messy, so agree with you and went with option 2. @rossroberts-toast let me know if you have any concerns.