experimental: what if - interceptors

[bbasata]

Description

The ongoing experimental theme: I "think" by trying things & sharing them 😃

This pull request proposes a way for a logical provider to "intercept" a request and return a modified context.

As an example, we'll consider a combined SDK+Framework provider, with a List Resource in the Framework logical provider and a Resource in the SDK logical provider. When mux handles a ListResource request, the SDK provider's interceptor will decorate the context with Resource "stuff" – a schema map or even a schema.Resource.

Example: hashicorp/terraform-provider-azurerm#30122 (draft)

The List Resource in the Framework logical provider can use this Resource "stuff" to interact with existing provider logic.

Example: server_listresource_tfprotov5_test.go#L80-L82 (draft)

And mux and Framework remain blissfully decoupled from SDK.

I've borrowed the name "interceptors" from gRPC.

cc: @stephybun

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

None.

[bbasata]

Suggested change

	ctx = i.BeforeListResource(ctx, req)
	ctx = i.Before(ctx, ListResource, req)