Permit Multibinds with MembersInjector values

[damianw]

The MultibindsMethodValidator prevents Multibinds methods from using Producer, Produced, Lazy, Provider, and MembersInjector as a Map value type or a Set element type. However, out of all of these, MembersInjector does not actually produce or access any instances; instead, it operates on an instance provided as an argument. Therefore, using it as a Map or Set value type is actually quite different than any of the rest.

It's actually already possible multi-bind a Set or Map with MembersInjector values, but not to declare such a binding with Multibinds. This PR changes the validator to allow such binding declarations, and adds additional tests to verify (and demonstrate) that this works as intended.

[Chang-Eric]

Thanks for the PR and sorry for the delay here. Looking into this, I think we're actually just completely missing validation on the @IntoSet and @IntoMap types. I tried doing an @Provides @IntoMap that returns a Provider and it worked (or got farther than it should have), even though it really shouldn't be allowed.

I think it should be okay to allow MembersInjector though for maps, so what I'll do is I'll merge your PR in for the tests as disabled and then probably send a follow up to add the checking and enablement in?

[damianw]

Sounds great, thanks! Appreciate your looking into it.

[Chang-Eric]

Also note the preceding change 15a30ca that adds validation for @IntoSet/@IntoMap bindings