initial MailMessage packet work and testing

common/src/main/scala/net/psforever/packet/GamePacketOpcode.scala

@@ -605,7 +605,7 @@ object GamePacketOpcode extends Enumeration {
 
     // OPCODES 0xf0-f3
     case 0xf0 => noDecoder(QueueTimedHelpMessage)
-    case 0xf1 => noDecoder(MailMessage)
+    case 0xf1 => game.MailMessage.decode
     case 0xf2 => noDecoder(GameVarUpdate)
     case 0xf3 => noDecoder(ClientCheatedMessage)
     case default => noDecoder(opcode)

common/src/main/scala/net/psforever/packet/game/MailMessage.scala

@@ -0,0 +1,35 @@
+// Copyright (c) 2017 PSForever
+package net.psforever.packet.game
+
+import net.psforever.packet.{GamePacketOpcode, Marshallable, PacketHelpers, PlanetSideGamePacket}
+import scodec.Codec
+import scodec.codecs._
+
+/**
+  * Dispatched from the server, sending a "priority message" to the given client's avatar.
+  * The messaging inbox is generally accessible through the use of `alt`+`i`.
+  * It is also made accessible through use of an icon in the lower right corner when there is an outstanding message.<br>
+  * <br>
+  * Exploration:<br>
+  * How does the PlanetSide Classic mail system work?
+  * At the moment, it only seems possible to receive and read mail from the server.
+  * @param sender the name of the player who sent the mail
+  * @param subject the subject
+  * @param message the message
+  */
+final case class MailMessage(sender : String,
+                             subject : String,
+                             message : String
+                            ) extends PlanetSideGamePacket {
+  type Packet = MailMessage
+  def opcode = GamePacketOpcode.MailMessage
+  def encode = MailMessage.encode(this)
+}
+
+object MailMessage extends Marshallable[MailMessage] {
+  implicit val codec : Codec[MailMessage] = (
+    ("sender" | PacketHelpers.encodedString) ::
+      ("subject" | PacketHelpers.encodedString) ::
+      ("message" | PacketHelpers.encodedString)
+    ).as[MailMessage]
+}