HTM-2136: Save keywords for layers

Author: matthijsln

src/main/java/org/tailormap/api/persistence/helper/GeoServiceHelper.java

@@ -276,6 +276,7 @@ private GeoServiceLayer toGeoServiceLayer(Layer l, List<? extends Layer> layers)
             .collect(Collectors.toList()))
         .queryable(l.isQueryable())
         .abstractText(l.get_abstract())
+        .keywords(l.getKeywords() == null ? Set.of() : Set.copyOf(List.of(l.getKeywords())))
         .children(l.getLayerChildren().stream()
             .map(layers::indexOf)
             .map(String::valueOf)

src/main/resources/openapi/persistence-schemas.yaml

@@ -504,6 +504,11 @@ components:
           type: boolean
         abstractText:
           type: string
+        keywords:
+          type: array
+          items:
+            type: string
+          uniqueItems: true
         children:
           type: array
           items: