Generate Unique ID for the State w/o relying on Caller to generate it

[katfang]

Is your feature request related to a problem? Please describe.

It seems like right now, it is the caller's responsibility to generate a unique ID for the State, b/c without an ID, it's not even possible to do anything with the state.

Sometimes, I don't really care what the State ID is, just that it is unique.

My code looks something like this

service MoveMethods {
    // Caller is responsible for making the id
    rpc Store(MoveRequest) returns (EmptyResponse) {
        option (rbt.v1alpha1.method).writer = {}
    }

    rpc Get(EmptyRequest) returns (cheaoss.v1.Move) {
        option (rbt.v1alpha1.method).reader = {}
    }

    rpc Clear(EmptyRequest) returns (EmptyResponse) {
        option (rbt.v1alpha1.method).writer = {}
    }
}

Describe the solution you'd like

Ideally Store(Move) would generate it's own unique ID and return it as the response.

Describe alternatives you've considered
It "seems fine" to have the caller generate a UUIDv4, and it is often useful for the caller to generate an ID that also serves as a way to "search" for the object, but sometimes I actually just don't care OR I actively want something non-guessable but want to ensure uniqueness.

For now, I'll generate a UUIDv4.

Additional context
Add any other context or screenshots about the feature request here.

[rjhuijsman]

This is currently (only) supported when using an explicit constructor:

Calling an explicit constructor will generate a new unique ID (a UUID) for the constructed state. Alternatively, you can specify an ID explicitly upon construction by passing it after context.

If you're using an implicit constructor (as in the example in the opening post) however, we don't have that feature currently. Seems like we should find a place for it in the API.