refactor: Add IrohDeployer

- This splits the existing deploy_iroh_relay() routine into methods
  for the install, configure, and activate stages.

cmdeploy/src/cmdeploy/__init__.py

@@ -802,7 +802,13 @@ def deploy_mtail(config):
     )
 
 
-def deploy_iroh_relay(config) -> None:
+class IrohDeployer(Deployer):
+    def __init__(self, *, enable_iroh_relay, **kwargs):
+        super().__init__(**kwargs)
+        self.enable_iroh_relay = enable_iroh_relay
+
+    @staticmethod
+    def install_impl():
         (url, sha256sum) = {
             "x86_64": (
                 "https://github.com/n0-computer/iroh/releases/download/v0.35.0/iroh-relay-v0.35.0-x86_64-unknown-linux-musl.tar.gz",
@@ -819,8 +825,6 @@ def deploy_iroh_relay(config) -> None:
             packages=["curl"],
         )
 
-    need_restart = False
-
         existing_sha256sum = host.get_fact(Sha256File, "/usr/local/bin/iroh-relay")
         if existing_sha256sum != sha256sum:
             server.shell(
@@ -830,8 +834,14 @@ def deploy_iroh_relay(config) -> None:
                     "chmod 755 /usr/local/bin/iroh-relay",
                 ],
             )
-        need_restart = True
 
+            #
+            # This will set need_restart when called from an object's
+            # install() method.
+            #
+            return True
+
+    def configure_impl(self):
         systemd_unit = files.put(
             name="Upload iroh-relay systemd unit",
             src=importlib.resources.files(__package__).joinpath("iroh-relay.service"),
@@ -840,7 +850,7 @@ def deploy_iroh_relay(config) -> None:
             group="root",
             mode="644",
         )
-    need_restart |= systemd_unit.changed
+        self.need_restart |= systemd_unit.changed
 
         iroh_config = files.put(
             name="Upload iroh-relay config",
@@ -850,15 +860,17 @@ def deploy_iroh_relay(config) -> None:
             group="root",
             mode="644",
         )
-    need_restart |= iroh_config.changed
+        self.need_restart |= iroh_config.changed
 
+    def activate_impl(self):
         systemd.service(
             name="Start and enable iroh-relay",
             service="iroh-relay.service",
             running=True,
-        enabled=config.enable_iroh_relay,
+            enabled=self.enable_iroh_relay,
-        restarted=need_restart,
+            restarted=self.need_restart,
         )
+        self.need_restart = False
 
 
 def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
@@ -879,6 +891,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
         )
 
     unbound_deployer = UnboundDeployer()
+    iroh_deployer = IrohDeployer(enable_iroh_relay=config.enable_iroh_relay)
     opendkim_deployer = OpendkimDeployer(mail_domain=mail_domain)
 
     # Dovecot should be started before Postfix
@@ -891,6 +904,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
 
     all_deployers = [
         unbound_deployer,
+        iroh_deployer,
         opendkim_deployer,
         dovecot_deployer,
         postfix_deployer,
@@ -970,7 +984,9 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
     unbound_deployer.configure()
     unbound_deployer.activate()
 
-    deploy_iroh_relay(config)
+    iroh_deployer.install()
+    iroh_deployer.configure()
+    iroh_deployer.activate()
 
     # Deploy acmetool to have TLS certificates.
     tls_domains = [mail_domain, f"mta-sts.{mail_domain}", f"www.{mail_domain}"]