Listener specific Custom error page configuration

[bganguly14]

Is your feature request related to a problem? Please describe. At present if we want to set any Custom error page, we have to set it on AppGw label. But that does not fulfil the requirement of multi tenant clusters where each application has its own custom error page. Currently, there are no annotations through which we can configure the Custom Error page per listener.

Describe the solution you'd like As all the properties of an AGIC-enabled AppGw are controlled from the annotations, there should be some annotations to set custom error pages per listener.