Add placeholder text for group/course filter

aleksis/apps/alsijil/frontend/components/Coursebook.vue

@@ -17,7 +17,9 @@
           filled
           dense
           hide-details
+          :placeholder="$t('alsijil.coursebook.filter.filter_for_obj')"
           :loading="selectLoading"
+          :value="currentObj"
           @input="changeSelection"
           @click:clear="changeSelection"
       />
@@ -167,6 +169,9 @@ export default {
         ...this.courses.map((course) => ({ type: "course", ...course })),
       ];
     },
+    currentObj() {
+      return this.selectable.find((o) => o.type === this.objType && o.id === this.objId);
+    },
     selectLoading() {
       return this.$apollo.queries.groups.loading || this.$apollo.queries.courses.loading;
     }

aleksis/apps/alsijil/frontend/messages/de.json

@@ -51,7 +51,8 @@
       "filter": {
         "own": "Nur eigene Stunden anzeigen",
         "groups": "Klassen",
-        "courses": "Kurse"
+        "courses": "Kurse",
+        "filter_for_obj": "Nach Klasse und Kurs filtern"
       }
     }
   }

aleksis/apps/alsijil/frontend/messages/en.json

@@ -51,7 +51,8 @@
       "filter": {
         "own": "Only show own lessons",
         "groups": "School classes",
-        "courses": "Courses"
+        "courses": "Courses",
+        "filter_for_obj": "Filter for school class and course"
       }
     }
   }