Use Value for ResolveObjectResponse value type.

[toddbaert]

If the discussion here is implemented, I think we want to change ResolveObjectResponse from:

message ResolveObjectResponse {
    google.protobuf.Struct value = 1;
    string reason = 2;
    string variant = 3;
}

to:

message ResolveObjectResponse {
    google.protobuf.Value value = 1;
    string reason = 2;
    string variant = 3;
}

This allows us to return arrays (as well as other protobuf values) as the top level object in the object resolver.

Is there any objections or challenges to doing this? I've POC'd it in the flagd-java provider. Would it be reasonable in flagd?

@james-milligan @skyerus @beeme1mr

[james-milligan]

I have had play around with this library:
google.golang.org/protobuf/types/known/structpb
It seems pretty doable, we can cast the Value type into an interface{} and return this directly for the provider.
Within flagd we can just do the inverse

No objections from me