Require wait_for_stage parameter for Nexus Workflow Updates

[atol]

What was changed

Expose and require the wait_for_stage parameter to be explicitly set to ACCEPTED for Nexus Workflow Updates, instead of being hardcoded internally.

Why?

wait_for_stage is expected to be a required parameter because ACCEPTED is a non-obvious default that users should be aware of. This also aligns with the behaviour in the Go, Java, and .NET SDKs.

How was this tested

Add new test.

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[tconley1428]

Why are we requiring they pass a specific literal that we already know?

[atol]

@Quinn-With-Two-Ns has more context, but the gist is that ACCEPTED is an unintuitive default that has historically confused users, so we want to make them aware of the implications of the option (i.e. the worker needs to be running).

[tconley1428]

I don't think a nonintuitive default is really a good reason for a parameter, it's a good reason for a docstring. I don't think making every user and callsite provide this argument so that some users don't miss a docstring.

[atol]

Discussed offline. We plan to make ADMITTED the default in the future and want to avoid breaking users later.

[VegetarianOrc]

IMO we should cast to the enum rather than Any. Alternatively we can just add # type: ignore instead of casting. We might also consider allowing this internal method to accept the regular enum and requiring the literal on the public API as you've got here.

[atol]

Thanks for the suggestion! Updated the param type to WorkflowUpdateStage.