HttpUrl and AnyHttpUrl should have defaults for port when no port is specified

[davidolrik]

When creating a HttpUrl or AnyHttpUrl, the url scheme is required which should dictate a port if you don't specify one.
As it is now no port specified means port is None.

I propose that we look at the url scheme, and return 80 for http or 443 for https if port is not specified.

[samuelcolvin]

I haven't looked in detail, but I think coincidentally #2447 might make this possible.

My main concern is that converting an HttpUrl back to a string should result in the same string as the original.

If we always populate the port, we might end up with

'https://example.com/foobar' -> HttpUrl -> 'https://example.com:443/foobar'

which would be annoying

[davidolrik]

I wouldn't populate the port, just make the getter return the correct port when no port i specified.

[MihanixA]

Perhaps we could add hidden_fields member to hide a port field in HttpUrl for example?

[MihanixA]

Or display_port: bool to be specific

[MihanixA]

Committed to #2447