Add variable with stage information during build time

Problem

As an admin some times I need to identify the stage details during build time. This information is not available through build variables, requiring a call to

${bambooUrl}/rest/api/latest/search/jobs/${planKey}?searchTerm=${jobName}

Calling a rest API to get this information does not seem to be the best approach and even requires extra steps on filtering the results.

Suggested solution

Provide a variable that shares what is the stage name of the given build job running.