Allow constructing ServerName from String

[Keruspe]

Split the common part out of TryFrom<&str> and allow constructing a ServerName<'static> from a String like we do for DnsName when alloc feature is enabled.

This is useful when the domain name we want to connect to comes from an environmental source

[cpu]

allow constructing a ServerName<'static> from a String

Isn't this possible with the current API?

let servername = ServerName::try_from(my_string.as_str()).unwrap().to_owned();

Maybe there's a docs update to be done to make that pattern more discoverable.

[Keruspe]

Oh, I totally missed the to_owned, you're right

[djc]

That will make an extra allocation though, so it's less efficient?

[cpu]

Check out #21 and 1.0.1 - it should make this more ergonomic/easier to discover.

Thanks for raising the issue/opening a PR.