Add methods to set locatable, mutable flags in ResourceTypeBuildEvent

Problem/Motivation

Like other adjustments that are currently possible using ResourceTypeBuildEvent, I have a use case for having an entity type (one not backed by SQL storage) which is usable in json:api responses, but does not have automatic route generation or self URLs created.

The specific use case is using json:api as a gateway in front of the Instagram Basic Display API. This mostly works out of the box, but for a few things like the UUID not really being a UUID.

The rub comes when I want to be able to use jsonapi_resources as a de-facto replacement for the entityQuery-based controllers provided by json:api out of the box. I also need the entity type definition included in an openapi spec. I can't disable the resource type entirely, since that defeats the purpose of exposing it.

json:api's definition of mutable is "not a config entity" and locatable means "doesn't directly use null storage."

These determinations are made in static methods on the resource type repository and, like much of the json:api PHP API, is not easily overridden. I had to resort to some creative decoration pattern, especially since I'm also using both jsonapi_extras and jsonapi_cross_bundles.

The default rules for determining mutability and locatablility are correct in 99% of use cases. BUT, this is an area where it's extremely difficult to affect the resource type info. There is an event for making similar low-level rules (like disabling) and I think these two fields are candidates for similar treatment.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet