OZG-4949 OZG-5112 refactor abstract formservice; cleanup

...ent/libs/admin-settings/src/lib/admin-settings.linkrel.ts

...lient/libs/admin-settings/src/lib/admin-settings.model.ts

...ibs/admin-settings/src/lib/admin-settings.service.spec.ts

...ent/libs/admin-settings/src/lib/admin-settings.service.ts

...t/libs/admin-settings/src/lib/admin-settings.util.spec.ts

...client/libs/admin-settings/src/lib/admin-settings.util.ts

...n-settings/src/lib/configuration/configuration.linkrel.ts

alfa-client/libs/admin-settings/src/lib/error/error.model.ts

...h-container/postfach-form/postfach-form.component.spec.ts

.../postfach-container/postfach-form/postfach.formservice.ts

...avigation-item/postfach-navigation-item.component.spec.ts

.../libs/admin-settings/src/lib/postfach/postfach.linkrel.ts

...nt/libs/admin-settings/src/lib/postfach/postfach.model.ts

.../admin-settings/src/lib/postfach/postfach.service.spec.ts

.../libs/admin-settings/src/lib/postfach/postfach.service.ts

alfa-client/libs/admin-settings/test/admin-settings.ts

...t/libs/admin-settings/test/configuration/configuration.ts

alfa-client/libs/admin-settings/test/postfach/postfach.ts

...ibs/tech-shared/src/lib/resource/resource.service.spec.ts

...ent/libs/tech-shared/src/lib/resource/resource.service.ts