Allow redirects to http urls using other testing TLDs

[apexskier]

Related to #1021

Right now, hydra requires explicitly enabling http urls using the dangerous-allow-insecure-redirect-urls CLI parameter unless using a .localhost domain.

Our local setup chose to use .test over .localhost a long time ago, so this causes a bit of friction.

Given .localhost comes from RFC 2606, I'd like to propose adding .test as an enabled-by-default http callback URL, since it's also a reserved TLD used for testing.

I don't think it'd make sense to do this for .invalid or .example since they aren't intended for running code.

[vinckr]

Hey Cameron,
thanks for sharing!
I would like to gauge how many in the community would be interested in this. In general I think most people use .localhost, but that could be wrong.