x/build/cmd/relui, x/build/internal/workflow: come up with a mechanism for richer parameter metadata

[dmitshur]

Right now workflow parameters have a name, and always have type string.

workflow.Definition.ParameterNames() returns a slice of parameter names, which is sufficient to describe parameters today.

However, we may want to have additional metadata for parameters. For example:

• validation (at minimum, whether the zero value is allowed or not)
• documentation, sample values (might be part of doc)
• placeholder value
• parameter type (string, string slice, ...)

This is the tracking issue for this work.

CC @golang/release.

[dmitshur]

From a workflow's perspective, a parameter can be of type []string, but from relui's web UI perspective it can be a "0 or more large text areas" or "0 or more short single-line text boxes".

This suggests relui should make for a better place for storing such parameter metadata, as long as it doesn't get too much in the way of workflow self-description requirements.

[gopherbot]

Change https://go.dev/cl/404454 mentions this issue: internal/relui, internal/workflow: add parameter type support