[More forgiving custom domain input] Automagically remove prefix (https://) & suffixes (/et-EE) when inputing custom domains

When inserting custom domain, it might’ve been copied from somewhere, rather than user doing the troubleshooting work, it can all be done automagically.

If the input will look like:

https://my.super.custom.domain.example.com/et-EE/dashboard

Then the non-editable fields show as the input was instead:

my.super.custom.domain.example.com