refactor: Add EchobotDeployer

- This class is a special case because it has a dependency on the
  Postfix and Dovecot deployers.  When deciding whether to restart the
  echobot service, it needs to know whether the Postfix and Dovecot
  deployers restarted their services.  To support this dependency, the
  PostfixDeployer and DovecotDeployer objects are passed to the
  EchobotDeployer object, so it can check their was_restarted
  attributes.

cmdeploy/src/cmdeploy/__init__.py

@@ -934,6 +934,33 @@ class JournaldDeployer(Deployer):
         self.need_restart = False
 
 
+class EchobotDeployer(Deployer):
+    #
+    # This deployer depends on the dovecot and postfix deployers because
+    # it needs to base its decision of whether to restart the service on
+    # whether those two services were restarted.
+    #
+    def __init__(self, *, dovecot_deployer, postfix_deployer, **kwargs):
+        super().__init__(**kwargs)
+        self.dovecot_deployer = dovecot_deployer
+        self.postfix_deployer = postfix_deployer
+
+    @staticmethod
+    def install_impl():
+        apt.packages(
+            # required for setfacl for echobot
+            name="Install acl",
+            packages="acl",
+        )
+
+    def activate_impl(self):
+        systemd.service(
+            name="Restart echobot if postfix and dovecot were just started",
+            service="echobot.service",
+            restarted=self.postfix_deployer.was_restarted and self.dovecot_deployer.was_restarted,
+        )
+
+
 class ChatmailVenvDeployer(Deployer):
     def __init__(self, *, config, **kwargs):
         super().__init__(**kwargs)
@@ -1064,6 +1091,9 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
     nginx_deployer = NginxDeployer(config=config)
     rspamd_deployer = RspamdDeployer()
     fcgiwrap_deployer = FcgiwrapDeployer()
+    echobot_deployer = EchobotDeployer(
+        dovecot_deployer=dovecot_deployer, postfix_deployer=postfix_deployer
+    )
     journald_deployer = JournaldDeployer()
     mtail_deployer = MtailDeployer(mtail_address=config.mtail_address)
 
@@ -1080,6 +1110,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
         nginx_deployer,
         rspamd_deployer,
         fcgiwrap_deployer,
+        echobot_deployer,
         journald_deployer,
         mtail_deployer,
     ]
@@ -1136,12 +1167,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
     acmetool_deployer.configure()
     acmetool_deployer.activate()
 
-    apt.packages(
-        # required for setfacl for echobot
-        name="Install acl",
-        packages="acl",
-    )
-
+    echobot_deployer.install()
     mtasts_deployer.install()
     opendkim_deployer.install()
     postfix_deployer.install()
@@ -1178,18 +1204,14 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
     fcgiwrap_deployer.configure()
     opendkim_deployer.configure()
     opendkim_deployer.activate()
+    echobot_deployer.configure()
 
     dovecot_deployer.activate()
     postfix_deployer.activate()
     nginx_deployer.activate()
     rspamd_deployer.activate()
     fcgiwrap_deployer.activate()
-
-    systemd.service(
-        name="Restart echobot if postfix and dovecot were just started",
-        service="echobot.service",
-        restarted=postfix_deployer.was_restarted and dovecot_deployer.was_restarted,
-    )
+    echobot_deployer.activate()
 
     chatmail_deployer.configure()
     chatmail_deployer.activate()