Using legacy schema with legacy serializer/adapter errors in `shouldSerializeHasMany`

[BoussonKarel]

I've gone ahead and migrated some some resources off of model and to schema, but the JSON serializer is throwing an error when trying to decide whether it should serialize a hasMany:

warp-drive/warp-drive-packages/legacy/src/serializer/json.ts

Lines 964 to 967 in f3eb155

	// @ts-expect-error store is dynamically injected
	const schema = this.store.modelFor(snapshot.modelName);
	// @ts-expect-error store is dynamically injected
	const relationshipType = schema.determineRelationshipType(relationship, this.store);

determineRelationshipType exists on Model but not on my legacy resource schema.

This is probably overlooked because of the ts-expect-error above the line.

My legacy resource schema is made using withDefaults from @warp-drive/legacy/model/migration-support, so it's not a Model.