setting up predefined variable for username who who did the promotion

[creeram]

Proposed Feature

Currently, I see only the project, stage, and promotion predefined variables, which provide convenient access to the details of a Promotion. which can be referenced using ctx.projec,ctx.stage,ctx.promotion.

I am looking for a variable like ctx.username or ctx.triggeredby or ctx.promotedby.

Motivation

I'm using HTTP post message to post information of the promotion to a slack channel and i want to include the detail of that person who did the promotion.