refactor: Move turnserver out of ChatmailVenvDeployer

- Revised TurnDeployer to use _configure_remote_units() and
  _activate_remote_units().  This class no longer uses need_restart
  and daemon_reload attributes to keep track of state.  The activate
  stage of ChatmailVenvDeployer was unconditionally restarting the
  service every time, so we don't need to keep track of extra state in
  an attempt to avoid restarting it; we can just handle the
  unconditional restart in TurnDeployer.activate_impl().
- Removed turnserver from the unit list in ChatmailVenvDeployer.

cmdeploy/src/cmdeploy/__init__.py

@@ -763,7 +763,7 @@ class TurnDeployer(Deployer):
     def __init__(self, *, mail_domain, **kwargs):
         super().__init__(**kwargs)
         self.mail_domain = mail_domain
-        self.daemon_reload = False
+        self.units = ["turnserver"]
 
     @staticmethod
     def install_impl():
@@ -788,40 +788,11 @@ class TurnDeployer(Deployer):
                 ],
             )
 
-            #
-            # 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=self.mail_domain).encode()
-
-        systemd_unit = files.put(
-            name="Upload turnserver.service",
-            src=io.BytesIO(content),
-            dest="/etc/systemd/system/turnserver.service",
-            user="root",
-            group="root",
-            mode="644",
-        )
-        self.daemon_reload = systemd_unit.changed
-        self.need_restart |= systemd_unit.changed
+        _configure_remote_units(self.mail_domain, self.units)
 
     def activate_impl(self):
-        systemd.service(
-            name="Setup turnserver service",
-            service="turnserver.service",
-            running=True,
-            enabled=True,
-            restarted=self.need_restart,
-            daemon_reload=self.daemon_reload,
-        )
-        self.daemon_reload = False
-        self.need_restart = False
+        _activate_remote_units(self.units)
 
 
 class MtailDeployer(Deployer):
@@ -1018,7 +989,6 @@ class ChatmailVenvDeployer(Deployer):
             "echobot",
             "chatmail-metadata",
             "lastlogin",
-            "turnserver",
             "chatmail-expire",
             "chatmail-expire.timer",
             "chatmail-fsreport",