automatically tag broadcasts with the "Broadcast" study topic

modules/relay/src/main/RelayApi.scala

@@ -69,7 +69,8 @@ final class RelayApi(
           from = Study.From.Relay(none).some
         ),
         user
-      ) inject relay
+      ) >>
+      studyApi.addTopics(relay.studyId, List("Broadcast")) inject relay
   }
 
   def requestPlay(id: Relay.Id, v: Boolean): Funit = WithRelay(id) { relay =>

modules/study/src/main/Study.scala

@@ -71,6 +71,10 @@ case class Study(
   def light = LightStudy(isPublic, members.contributorIds)
 
   def topicsOrEmpty = topics | StudyTopics.empty
+
+  def addTopics(ts: StudyTopics) = copy(
+    topics = topics.fold(ts)(_ ++ ts).some
+  )
 }
 
 object Study {

modules/study/src/main/StudyApi.scala

@@ -740,6 +740,10 @@ final class StudyApi(
     }
   }
 
+  def addTopics(studyId: Study.Id, topics: List[String]) = sequenceStudy(studyId) { study =>
+    studyRepo.updateTopics(study addTopics StudyTopics.fromStrs(topics))
+  }
+
   def editStudy(studyId: Study.Id, data: Study.Data)(who: Who) = sequenceStudy(studyId) { study =>
     canActAsOwner(study, who.u) flatMap { asOwner =>
       data.settings.ifTrue(asOwner) ?? { settings =>

modules/study/src/main/StudyTopic.scala

@@ -29,6 +29,10 @@ case class StudyTopics(value: List[StudyTopic]) extends AnyVal {
   def diff(other: StudyTopics) = StudyTopics {
     value.toSet.diff(other.value.toSet).toList
   }
+
+  def ++(other: StudyTopics) = StudyTopics {
+    value.toSet.++(other.value.toSet).toList
+  }
 }
 
 object StudyTopics {