fix: resolve issues with things that can be offered

Fixes #41

src/core/things/DateSeries.ts

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018 StApps
+ * Copyright (C) 2018, 2019 StApps
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
  * Software Foundation, version 3.
@@ -17,6 +17,7 @@ import {
   SCAcademicPriceGroup,
   SCThingThatCanBeOffered,
   SCThingThatCanBeOfferedTranslatableProperties,
+  SCThingThatCanBeOfferedWithoutReferences,
 } from '../base/ThingThatCanBeOffered';
 import {SCThingMeta, SCThingType} from '../Thing';
 import {SCMetaTranslations, SCTranslations} from '../types/i18n';
@@ -38,8 +39,7 @@ export interface SCSportCoursePriceGroup extends SCAcademicPriceGroup {
 /**
  * A date without references
  */
-export interface SCDateSeriesWithoutReferences
-  extends SCThingThatCanBeOffered<SCSportCoursePriceGroup> {
+export interface SCDateSeriesWithoutReferences extends SCThingThatCanBeOfferedWithoutReferences {
   /**
    * Dates of the date series that are initially planned to be held
    */
@@ -76,7 +76,9 @@ export interface SCDateSeriesWithoutReferences
  *
  * @validatable
  */
-export interface SCDateSeries extends SCDateSeriesWithoutReferences, SCThingInPlace {
+export interface SCDateSeries extends SCDateSeriesWithoutReferences,
+  SCThingInPlace,
+  SCThingThatCanBeOffered<SCSportCoursePriceGroup> {
   /**
    * Event to which the date series belongs
    */
@@ -108,26 +110,26 @@ export class SCDateSeriesMeta extends SCThingMeta implements SCMetaTranslations<
    */
   fieldTranslations = {
     de: {
-      ... SCThingInPlaceMeta.getInstance().fieldTranslations.de,
+      ...SCThingInPlaceMeta.getInstance().fieldTranslations.de,
     },
     en: {
-      ... SCThingInPlaceMeta.getInstance().fieldTranslations.en,
+      ...SCThingInPlaceMeta.getInstance().fieldTranslations.en,
     },
   };
 
   /**
    * Translations of values of fields
    */
-  fieldValueTranslations  = {
+  fieldValueTranslations = {
     de: {
-      ... SCThingInPlaceMeta.getInstance().fieldValueTranslations.de,
+      ...SCThingInPlaceMeta.getInstance().fieldValueTranslations.de,
       dates: 'Einzeltermine',
       duration: 'Dauer',
       frequency: 'Wiederholung',
       type: 'Wiederholungreihe',
     },
     en: {
-      ... SCThingInPlaceMeta.getInstance().fieldValueTranslations.en,
+      ...SCThingInPlaceMeta.getInstance().fieldValueTranslations.en,
       type: SCThingType.DateSeries,
     },
   };