refactor(iroh-base): introduce an Arc into RelayUrl (#3065)

## Description

This makes the `clone`ing of `RelayUrl` much cheaper. 
It turned out the whole code base was already using the `RelayUrl` as an
immutable type already, so no changes otherwise necessary.

## Breaking Changes

<!-- Optional, if there are any breaking changes document them,
including how to migrate older code. -->

## Notes & open questions

<!-- Any notes, remarks or open questions you have to make about the PR.
-->

## Change checklist

- [x] Self-review.
- [x] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [x] Tests if relevant.
- [x] All breaking changes documented.

iroh-base/Cargo.toml

@@ -22,7 +22,7 @@ derive_more = { version = "1.0.0", features = ["display"], optional = true }
 url = { version = "2.5", features = ["serde"], optional = true }
 postcard = { version = "1", default-features = false, features = ["alloc", "use-std", "experimental-derive"], optional = true }
 rand_core = { version = "0.6.4", optional = true }
-serde = { version = "1", features = ["derive"] }
+serde = { version = "1", features = ["derive", "rc"] }
 thiserror = { version = "2", optional = true }
 
 # wasm

iroh-base/src/relay_url.rs

@@ -1,10 +1,12 @@
-use std::{fmt, ops::Deref, str::FromStr};
+use std::{fmt, ops::Deref, str::FromStr, sync::Arc};
 
 use serde::{Deserialize, Serialize};
 use url::Url;
+
 /// A URL identifying a relay server.
 ///
-/// This is but a wrapper around [`Url`], with a few custom tweaks:
+/// It is cheaply clonable, as the underlying type is wrapped into an `Arc`.
+/// The main type under the hood though is [`Url`], with a few custom tweaks:
 ///
 /// - A relay URL is never a relative URL, so an implicit `.` is added at the end of the
 ///   domain name if missing.
@@ -16,7 +18,7 @@ use url::Url;
 #[derive(
     Clone, derive_more::Display, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize,
 )]
-pub struct RelayUrl(Url);
+pub struct RelayUrl(Arc<Url>);
 
 impl From<Url> for RelayUrl {
     fn from(mut url: Url) -> Self {
@@ -31,7 +33,7 @@ impl From<Url> for RelayUrl {
                 url.set_host(Some(&domain)).ok();
             }
         }
-        Self(url)
+        Self(Arc::new(url))
     }
 }
 
@@ -55,7 +57,7 @@ impl FromStr for RelayUrl {
 
 impl From<RelayUrl> for Url {
     fn from(value: RelayUrl) -> Self {
-        value.0
+        Arc::unwrap_or_clone(value.0)
     }
 }
 

iroh-net-report/src/lib.rs

@@ -611,7 +611,7 @@ impl Actor {
                     self.handle_run_check(relay_map, opts, response_tx);
                 }
                 Message::ReportReady { report } => {
-                    self.handle_report_ready(report);
+                    self.handle_report_ready(*report);
                 }
                 Message::ReportAborted { err } => {
                     self.handle_report_aborted(err);
@@ -694,8 +694,8 @@ impl Actor {
         });
     }
 
-    fn handle_report_ready(&mut self, report: Box<Report>) {
-        let report = self.finish_and_store_report(*report);
+    fn handle_report_ready(&mut self, report: Report) {
+        let report = self.finish_and_store_report(report);
         self.in_flight_stun_requests.clear();
         if let Some(ReportRun { report_tx, .. }) = self.current_report_run.take() {
             report_tx.send(Ok(report)).ok();