The server uses underscores (_) as a delimiter for storing Parent and Child WfRunIds, like so: parent-id_child-id. This means that underscores should be treated as a special character and users should not be able to use them in their custom WfRunIds or we risk confusing the server.

Bug

If a user does execute a single WfRun with an underscore in the WfRunId, the server interprets the WfRun as being a child workflow run tied back to a parent workflow run.

Steps to Reproduce

1. Register a WfSpec with the server
2. Make a RunWf request for that WfSpec, with the WfRunId set to yoda_grogu
3. Search for the existing WfRuns under that WfSpec
4. The search should reveal that a workflow grogu was created, and that the workflow has a parent workflow of yoda

This is a problem for multiple reasons. Firstly, Yoda is not Grogu's parent. Secondly, the server now thinks that there should be a WfRun named yoda somewhere, even though it does not exist.