Zuul currently has a zuul/gated badge that can be linked e.g. in a
readme of a project. This is sufficient for many use cases. However if
a project has periodic jobs that do extended testing which is not
possible in check/gate this is not sufficient. For use cases like
those we can add support for dynamic badges in zuul itself.
Change-Id: I449fa9f38ca251522789b6075fbc876d21bd0200
5350525e65
