Custom navigation items: Improve target Single Column URL

[2sh]

Is your feature request related to a problem? Please describe.

Making use of the custom navigation feature and making the URL a path outside of /icingaweb2 but on the same domain, while the target "Single Column" opens the specified URL on the right of the Icingaweb menu, the URL of the current page also changes to that specified URL. This means that when you refresh the page (or go back to the page tab after the browser has discarded it for whatever reason), it loads the specified URL, taking you out of the Icingaweb view entirely. This can be rather confusing.

Describe the solution you'd like

When navigating to the custom navigation item with target "Single Column", let the the URL be an internal URL, something under "/icingaweb2/navigation/" perhaps.

[2sh]

I've now realised Icingaweb puts the URL after "iframe?url=" if it's under a different domain and changes it to a relative path if on the same domain. This causes the previously mentioned behaviour if that path is outside of the /icingaweb2 path though, somewhat of a bug really. A workaround I'm using now is to specify the URL with "iframe?url=" before it.

[nilmerg]

and changes it to a relative path if on the same domain

eehm, no. I cannot reproduce this nor can I find any sign of such behavior in the code responsible for this.

Configuring an item with the url http://localhost/test while on localhost/icingaweb2 shows this: