Rest HL client: Add get license action
Continues to use String instead of a more complex License class to
hold the license text similarly to put license.
Relates #29827
In the HL REST client we replace the License object with a string, because of
complexity of this class. It is also not really needed on the client side since
end-users are not interacting with the license besides passing it as a string
to the server.
Relates #29827
Yannick Welsch
Igor Motov
debadair