Implement Keep Alive messages.

src/requests/keepalive.cr

@@ -0,0 +1,11 @@
+class AuthD::Request
+	IPC::JSON.message KeepAlive, 250 do
+		def initialize()
+		end
+
+		def handle(authd : AuthD::Service, fd : Int32)
+			Response::KeepAlive.new
+		end
+	end
+	AuthD.requests << KeepAlive
+end

src/responses/keepalive.cr

@@ -0,0 +1,7 @@
+class AuthD::Response
+	IPC::JSON.message KeepAlive, 250 do
+		def initialize()
+		end
+	end
+	AuthD.responses << KeepAlive
+end