refactor: change meta class structure to include types.

Introduce requiredness of translations via implemented interface.

src/core/things/ToDo.ts

@@ -12,8 +12,12 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
-import {SCThingWithCategoriesSpecificValues, SCThingWithCategoriesWithoutReferences} from '../base/ThingWithCategories';
+import {
+  SCThingWithCategoriesSpecificValues,
+  SCThingWithCategoriesWithoutReferences,
+  SCThingWithCategoriesWithoutReferencesMeta} from '../base/ThingWithCategories';
 import {SCThingMeta, SCThingType} from '../Thing';
+import {SCMetaTranslations} from '../types/i18n';
 import {SCISO8601Date} from '../types/Time';
 
 /**
@@ -60,7 +64,36 @@ export enum SCToDoPriority {
 }
 
 /**
- * "To do" meta data
+ * Meta information about todo
  */
-export class SCToDoMeta extends SCThingMeta {
+export class SCToDoMeta extends SCThingMeta implements SCMetaTranslations<SCToDo> {
+  /**
+   * Translations of fields
+   */
+  fieldTranslations = {
+    de: {
+      ... SCThingWithCategoriesWithoutReferencesMeta.getInstance<string,
+            SCThingWithCategoriesSpecificValues>().fieldTranslations.de,
+    },
+    en: {
+      ... SCThingWithCategoriesWithoutReferencesMeta.getInstance<string,
+            SCThingWithCategoriesSpecificValues>().fieldTranslations.en,
+    },
+  };
+
+  /**
+   * Translations of values of fields
+   */
+  fieldValueTranslations  = {
+    de: {
+      ... SCThingWithCategoriesWithoutReferencesMeta.getInstance<string,
+            SCThingWithCategoriesSpecificValues>().fieldValueTranslations.de,
+      type: 'ToDo',
+    },
+    en: {
+      ... SCThingWithCategoriesWithoutReferencesMeta.getInstance<string,
+            SCThingWithCategoriesSpecificValues>().fieldValueTranslations.en,
+      type: SCThingType.ToDo,
+    },
+  };
 }