feat: 参加・退出メッセージを出すsubsystemを実装

src/main/scala/com/github/unchama/seichiassist/SeichiAssist.scala

@@ -497,6 +497,9 @@ class SeichiAssist extends JavaPlugin() {
   private lazy val gridRegionSystem: subsystems.gridregion.System[IO, Player, Location] =
     subsystems.gridregion.System.wired[IO, SyncIO].unsafeRunSync()
 
+  private lazy val joinAndQuitMessenger: Subsystem[IO] =
+    subsystems.joinandquitmessenger.System.wired[IO]
+
   private lazy val wiredSubsystems: List[Subsystem[IO]] = List(
     mebiusSystem,
     expBottleStackSystem,
@@ -534,7 +537,8 @@ class SeichiAssist extends JavaPlugin() {
     consumeGachaTicketSystem,
     openirontrapdoor.System.wired,
     gridRegionSystem,
-    breakSkillTargetConfigSystem
+    breakSkillTargetConfigSystem,
+    joinAndQuitMessenger
   )
 
   private lazy val buildAssist: BuildAssist = {

src/main/scala/com/github/unchama/seichiassist/subsystems/joinandquitmessenger/System.scala

@@ -0,0 +1,15 @@
+package com.github.unchama.seichiassist.subsystems.joinandquitmessenger
+
+import com.github.unchama.seichiassist.meta.subsystem.Subsystem
+import com.github.unchama.seichiassist.subsystems.joinandquitmessenger.bukkit.JoinAndQuitListeners
+import org.bukkit.event.Listener
+
+object System {
+
+  def wired[F[_]]: Subsystem[F] = {
+    new Subsystem[F] {
+      override val listeners: Seq[Listener] = Seq(new JoinAndQuitListeners)
+    }
+  }
+
+}

src/main/scala/com/github/unchama/seichiassist/subsystems/joinandquitmessenger/bukkit/JoinAndQuitListeners.scala

@@ -0,0 +1,18 @@
+package com.github.unchama.seichiassist.subsystems.joinandquitmessenger.bukkit
+
+import com.github.unchama.seichiassist.subsystems.joinandquitmessenger.domain.Messages
+import org.bukkit.ChatColor
+import org.bukkit.event.Listener
+import org.bukkit.event.player.{PlayerJoinEvent, PlayerQuitEvent}
+
+class JoinAndQuitListeners extends Listener {
+
+  def onJoin(event: PlayerJoinEvent): Unit = {
+    event.setJoinMessage(s"${ChatColor.GRAY}${Messages.joinMessage(event.getPlayer.getName)}")
+  }
+
+  def onQuit(event: PlayerQuitEvent): Unit = {
+    event.setQuitMessage(Messages.quitMessage(event.getPlayer.getName))
+  }
+
+}

src/main/scala/com/github/unchama/seichiassist/subsystems/joinandquitmessenger/domain/Messages.scala

@@ -0,0 +1,10 @@
+package com.github.unchama.seichiassist.subsystems.joinandquitmessenger.domain
+
+object Messages {
+
+  def joinMessage(playerName: String): String = s"$playerName がログインしました"
+
+  // Note: 整地鯖では退出メッセージを表示しない
+  def quitMessage(playerName: String): String = ""
+
+}