https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules "The compiler is more likely to get the default semantics right and you cannot implement these functions better than the compiler."
This was used in a lot of places, so this patch makes liberal use of ErrorOr<T>::release_value_but_fixme_should_propagate_errors().
Asking the user for a password is a fairly common thing, so let's have a reusable GUI dialog for it! This first iteration only supports having pre-filled "server" and "username" fields. This can obviously be made more flexible as needs arise. :^)