feat: make SCDateSeries.frequency compliant with schema.org

src/things/date-series.ts

@@ -65,9 +65,9 @@ export interface SCDateSeriesWithoutReferences
   /**
    * Frequency of the date series
    *
-   * @keyword
+   * @filterable
    */
-  frequency: string;
+  repeatFrequency?: SCISO8601Duration;
 
   /**
    * Translated properties
@@ -131,7 +131,7 @@ export class SCDateSeriesMeta
       duration: 'Dauer',
       event: 'Event',
       exceptions: 'Ausnahmen',
-      frequency: 'Frequenz',
+      repeatFrequency: 'Frequenz',
       performers: 'Vortragende',
     },
     en: {
@@ -143,7 +143,7 @@ export class SCDateSeriesMeta
       duration: 'duration',
       event: 'event',
       exceptions: 'exceptions',
-      frequency: 'frequency',
+      repeatFrequency: 'frequency',
       performers: 'performers',
     },
   };

test/resources/DateSeries.1.json

@@ -22,7 +22,7 @@
         }
       }
     },
-    "frequency": "once",
+    "repeatFrequency": "P1W",
     "dates": [
       "2016-04-15T17:00:00+00:00"
     ],

test/resources/DateSeries.2.json

@@ -23,7 +23,6 @@
       "name": "EMH 225",
       "floorName": "2"
     },
-    "frequency": "once",
     "dates": [
       "2016-04-12T11:00:00+00:00"
     ],

test/resources/DateSeries.3.json

@@ -23,7 +23,6 @@
       "name": "EMH 225",
       "floorName": "2"
     },
-    "frequency": "once",
     "dates": [
       "2016-04-12T11:00:00+00:00"
     ],