Add support for attributes

I ported the annotation, but I removed "class" because attributes already have that.

Forgot to wire up the attribute; that's fixed now and I think this is ready to go.

Thanks for this.

I wonder if we should to the BC way, supporting both annotaatinos and attributes. But perhaps since we are the source of the manager only supporting getting things by annotations is fine. Do you agree?

The annotation class is still there, so annotations are still supported for people who have written their own plugins on top of JSON:API Extras and are using annotations.

As for the plugins in this module, it is fine to convert them to attributes now because the module's composer.json already has "php": ">=8.1", so attributes will definitely be supported (attribute support is from 8.1). So I don't think this should break anything for anyone.

Yeah same cocnclusion here. Thanks!

Automatically closed - issue fixed for 2 weeks with no activity.