Add Request::name() method returning SMTP command name

[edevil]

Summary

Add a name() method to Request<T> that returns the SMTP command name as a &'static str (e.g. "EHLO", "MAIL", "RCPT", "QUIT").

This is useful for logging, tracing, and metrics where consumers need a human-readable label for the command variant. Currently every consumer of this crate has to write their own match expression to map request variants to command name strings — this is trivial boilerplate that belongs in the library.

Example

let req = Request::parse(&mut input.iter())?.into_owned();
println!("Received command: {}", req.name()); // "MAIL", "RCPT", "EHLO", etc.

Changes

• Added impl<T> Request<T> block with pub fn name(&self) -> &'static str in src/lib.rs
• Added request_name test in src/request/parser.rs