Iām incredibly late to the party here, but the good news is that 8.0.7 will allow authentication to be set per method, which of course implies that you could not do this before.
The change should be on the nightly if you wanted to start taking advantage of it, otherwise December 20th is the target for 8.0.7 release.
Yeah, the workaround was a pretty messy solution that involved hacking the Jetty configuration files included with Ignition, so looking forward to having proper support per-method.