add api definition for global motd

src/main/scala/de/thm/arsnova/api/GlobalMotdApi.scala

 package de.thm.arsnova.api
 
-/**
-  * Created by tekay on 3/22/17.
-  */
+import de.thm.arsnova.services.GlobalMotdService
+import de.thm.arsnova.models._
+import de.thm.arsnova.hateoas.{ApiRoutes, ResourceAdapter, Link}
+
+import scala.concurrent.ExecutionContext.Implicits.global
+import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
+import akka.http.scaladsl.server.Directives._
+import spray.json._
+
+/*
+The API Interface regarding global messages.
+Only an admin should post these motd
+ */
 trait GlobalMotdApi {
+  // protocol for serializing data
+  import de.thm.arsnova.mappings.GlobalMotdJsonProtocol._
+
+  // add the "top level" endpoint to ApiRoutes
+  ApiRoutes.addRoute("globalmotd", "globalmotd")
+
+  // function to generate the model links
+  def globalMotdLinks(motd: GlobalMotd): Seq[Link] = {
+    Seq(
+      Link("self", s"/${ApiRoutes.getRoute("globalmotd")}/${motd.id.get}")
+    )
+  }
+
+  // the HATEOAS Adapter
+  val globalMotdAdapter = new ResourceAdapter[GlobalMotd](globalMotdFormat, globalMotdLinks)
 
+  val globalMotdApi = pathPrefix(ApiRoutes.getRoute("globalmotd")) {
+    pathEndOrSingleSlash {
+      get {
+        parameter("audience".as[String]) { audience =>
+          complete (GlobalMotdService.getByAudience(audience).map(globalMotdAdapter.toResources(_)))
+        }
+      } ~
+      post {
+        entity(as[GlobalMotd]) { motd =>
+          complete (GlobalMotdService.create(motd).map(_.toJson))
+        }
+      }
+    } ~
+    pathPrefix(IntNumber) { motdId =>
+      pathEndOrSingleSlash {
+        get {
+          complete (GlobalMotdService.getById(motdId).map(globalMotdAdapter.toResource(_)))
+        } ~
+        put {
+          entity(as[GlobalMotd]) { motd =>
+            complete (GlobalMotdService.update(motd).map(_.toJson))
+          }
+        } ~
+        delete {
+          complete (GlobalMotdService.delete(motdId).map(_.toJson))
+        }
+      }
+    }
+  }
 }