Port-based multitenancy data can't be entered at configuration time

Current situation:

I'm trying to create a second bench on a system with the domain "bv-dev" using another port, since currently I have no control over DNS in the LAN.

So New Site > Site name: "bv-dev:8010" refuses to create the site, complaining: "Site name must be a valid hostname.", thus the port cannot be entered at New Site name configuration moment and the configuration stops here. While the error message looks technically correct, it might be unnecessarily restrictive to accomodate this second-bench-on-some-hostname creation intention.

OTOH, New Site > Site name: "bv-dev" > Create Site also refuses to create the site, complaining: "The site name is already in use.", also stopping here. Thus the "obvious workaround", e.g. first creating the site and then reconfiguring the site's port doesn't work either.

Workaround:

Use another hostname and fiddle with user's hosts files, but that's not very practical (depending on the number and position of users / testers / size of a showcase audience affected).

Expected result:

An easy way to enter a hostname:port combo in the New Site dialog and it being taken care of by pilot, the bench and nginx configuration it creates, and the framework's routing.

Start by tracing the New Site dialog's hostname validation and the configuration generated for pilot, the bench, nginx, and framework routing. Define how hostname:port input should be represented across those components, then verify that a second bench can be created and accessed on the requested port without requiring a different hostname.

Written by the indexing model from the issue text.