refactor: Add TurnDeployer

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

cmdeploy/src/cmdeploy/__init__.py

@@ -756,7 +756,14 @@ def check_config(config):
     return config
 
 
-def deploy_turn_server(config):
+class TurnDeployer(Deployer):
+    def __init__(self, *, mail_domain, **kwargs):
+        super().__init__(**kwargs)
+        self.mail_domain = mail_domain
+        self.daemon_reload = False
+
+    @staticmethod
+    def install_impl():
         (url, sha256sum) = {
             "x86_64": (
                 "https://github.com/chatmail/chatmail-turn/releases/download/v0.3/chatmail-turn-x86_64-linux",
@@ -768,8 +775,6 @@ def deploy_turn_server(config):
             ),
         }[host.get_fact(facts.server.Arch)]
 
-    need_restart = False
-
         existing_sha256sum = host.get_fact(Sha256File, "/usr/local/bin/chatmail-turn")
         if existing_sha256sum != sha256sum:
             server.shell(
@@ -779,12 +784,18 @@ def deploy_turn_server(config):
                     "chmod 755 /usr/local/bin/chatmail-turn",
                 ],
             )
-        need_restart = True
 
+            #
+            # This will set need_restart when called from an object's
+            # install() method.
+            #
+            return True
+
+    def configure_impl(self):
         source_path = importlib.resources.files(__package__).joinpath(
             "service", "turnserver.service.f"
         )
-    content = source_path.read_text().format(mail_domain=config.mail_domain).encode()
+        content = source_path.read_text().format(mail_domain=self.mail_domain).encode()
 
         systemd_unit = files.put(
             name="Upload turnserver.service",
@@ -794,16 +805,20 @@ def deploy_turn_server(config):
             group="root",
             mode="644",
         )
-    need_restart |= systemd_unit.changed
+        self.daemon_reload = systemd_unit.changed
+        self.need_restart |= systemd_unit.changed
 
+    def activate_impl(self):
         systemd.service(
             name="Setup turnserver service",
             service="turnserver.service",
             running=True,
             enabled=True,
-        restarted=need_restart,
+            restarted=self.need_restart,
-        daemon_reload=systemd_unit.changed,
+            daemon_reload=self.daemon_reload,
         )
+        self.daemon_reload = False
+        self.need_restart = False
 
 
 class MtailDeployer(Deployer):
@@ -1105,6 +1120,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
     tls_domains = [mail_domain, f"mta-sts.{mail_domain}", f"www.{mail_domain}"]
 
     chatmail_deployer = ChatmailDeployer(mail_domain=mail_domain)
+    turn_deployer = TurnDeployer(mail_domain=mail_domain)
     unbound_deployer = UnboundDeployer()
     iroh_deployer = IrohDeployer(enable_iroh_relay=config.enable_iroh_relay)
 
@@ -1133,6 +1149,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
 
     all_deployers = [
         chatmail_deployer,
+        turn_deployer,
         unbound_deployer,
         iroh_deployer,
         acmetool_deployer,
@@ -1162,7 +1179,9 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
 
     chatmail_deployer.install()
 
-    deploy_turn_server(config)
+    turn_deployer.install()
+    turn_deployer.configure()
+    turn_deployer.activate()
 
     port_services = [
         (["master", "smtpd"], 25),