Allow License info to be available via REST

There seems not to be a way to retrieve license info in Confluence via REST.

It should be added as a REST api end-point

JIRA and Bitbucket (as well UPM provide this end-point today)

I have found three different (private) end-points in Confluence:

• license/1.0/license/maxUsers
• license/1.0/license/remainingSeats
• license/1.0/license/userCount

It would be a great addition if the end-point:

* license/1.0/license

also was available, including data such as:

• Expiration date
• License Key

This is a bit related to CONF-43007 which deals with Application info available in REST