refactor: change meta class structure to include types.

Introduce requiredness of translations via implemented interface.

src/core/things/Ticket.ts

@@ -12,8 +12,9 @@
  * 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 {SCThingInPlace} from '../base/ThingInPlace';
+import {SCThingInPlace, SCThingInPlaceMeta} from '../base/ThingInPlace';
 import {SCThing, SCThingMeta, SCThingType} from '../Thing';
+import {SCMetaTranslations} from '../types/i18n';
 import {SCISO8601Duration} from '../types/Time';
 
 /**
@@ -56,11 +57,30 @@ export interface SCTicket extends SCTicketWithoutReferences, SCThingInPlace {
 /**
  * Meta information about a ticket
  */
-export class SCTicketMeta extends SCThingMeta {
-  static fieldValueTranslations = {
-    ...SCThingMeta.fieldValueTranslations,
+export class SCTicketMeta extends SCThingMeta implements SCMetaTranslations<SCTicket> {
+  /**
+   * Translations of fields
+   */
+  fieldTranslations = {
     de: {
+      ... SCThingInPlaceMeta.getInstance().fieldTranslations.de,
+    },
+    en: {
+      ... SCThingInPlaceMeta.getInstance().fieldTranslations.en,
+    },
+  };
+
+  /**
+   * Translations of values of fields
+   */
+  fieldValueTranslations  = {
+    de: {
+      ... SCThingInPlaceMeta.getInstance().fieldValueTranslations.de,
       type: 'Ticket',
     },
+    en: {
+      ... SCThingInPlaceMeta.getInstance().fieldValueTranslations.en,
+      type: SCThingType.Ticket,
+    },
   };
 }