Document VSA stage using automated webhook data labeling

What does this MR do and why?

Related to this customer problem:

"One of my customers wants to calculate the time it takes to make an application release available for production: Start date to be defined according to Gitlab possibilities :

date of the first commit on the 1st feature branch associated with the relase candidate (RC branch), itself associated with the final release (master/main branch) ?

date of the first merge request for the first feature on the RC branch (release candidate), associated with the final release on the master/main branch.

End date: date on which the application release goes into production.

We think is a value stream analytics use case, however we cannot find a way to calculate the date especially for the date on which the app release goes into prod. Any ideas/suggestions?"

And related to this comment - &9939 (comment 1935112874)

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