[FeatureRequest] Add RPC command to send output bindings in advance of InvocationResponse

[JustinGrote]

Issue

If a worker function wants to, say, write to a table output binding, and there is a problem with that binding, there is no way to inform the worker function that the table binding is incorrect during execution so that it can take appropriate action, therefore CreateIfNotExists and other patterns are not possible without leveraging direct SDKs, which kind of defeats the point of using outputbinding in the first place.

Recommended Resolution

Allow workers to submit Output Bindings ahead of final InvocationResponse, and the host can return an immediate result to the worker so that the worker can inform the function if required so it can take appropriate action if there is a problem.

This would be an RPC function definition like SubmitOutputBinding or something.

References

Azure/azure-functions-powershell-worker#284