refactor: change meta class structure to include types.

Introduce requiredness of translations via implemented interface.

src/core/things/Video.ts

@@ -12,9 +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 {SCCreativeWork, SCCreativeWorkWithoutReferences} from '../base/CreativeWork';
+import {SCCreativeWork, SCCreativeWorkMeta, SCCreativeWorkWithoutReferences} from '../base/CreativeWork';
 import {SCThingMeta, SCThingType} from '../Thing';
-import {SCLanguage} from '../types/i18n';
+import {SCLanguage, SCMetaTranslations} from '../types/i18n';
 import {SCISO8601Duration} from '../types/Time';
 import {SCPersonWithoutReferences} from './Person';
 
@@ -114,19 +114,33 @@ export interface SCVideo extends SCCreativeWork, SCVideoWithoutReferences {
   type: SCThingType.Video;
 }
 
-export class SCVideoMeta extends SCThingMeta {
-  static fieldValueTranslations = {
-    ...SCThingMeta.fieldValueTranslations,
+/**
+ * Meta information about a video
+ */
+export class SCVideoMeta extends SCThingMeta implements SCMetaTranslations<SCVideo> {
+  /**
+   * Translations of fields
+   */
+  fieldTranslations = {
     de: {
-      actors: 'Darsteller',
-      duration: 'Länge',
-      height: 'Höhe',
-      language: 'Sprache',
-      size: 'Größe',
-      sources: 'Quellen',
-      transcript: 'Abschrift',
+      ... SCCreativeWorkMeta.getInstance().fieldTranslations.de,
+    },
+    en: {
+      ... SCCreativeWorkMeta.getInstance().fieldTranslations.en,
+    },
+  };
+
+  /**
+   * Translations of values of fields
+   */
+  fieldValueTranslations  = {
+    de: {
+      ... SCCreativeWorkMeta.getInstance().fieldValueTranslations.de,
       type: 'Video',
-      width: 'Breite',
+    },
+    en: {
+      ... SCCreativeWorkMeta.getInstance().fieldValueTranslations.en,
+      type: SCThingType.Video,
     },
   };
 }