OZG-4948 OZG-5005 Create admin-settings library

alfa-client/apps/admin/src/app/app.module.ts

alfa-client/apps/admin/src/app/app.routes.ts

...ate-postfach-button/create-postfach-button.component.html

...-postfach-button/create-postfach-button.component.spec.ts

...pages/postfach/postfach-page/postfach-page.component.html

...es/postfach/postfach-page/postfach-page.component.spec.ts

...c/pages/postfach/postfach-page/postfach-page.component.ts

alfa-client/libs/admin-settings/.eslintrc.json

alfa-client/libs/admin-settings/README.md

alfa-client/libs/admin-settings/jest.config.ts

alfa-client/libs/admin-settings/project.json

alfa-client/libs/admin-settings/src/index.ts

...libs/admin-settings/src/lib/admin-settings.module.spec.ts

...ient/libs/admin-settings/src/lib/admin-settings.module.ts

...fach/postfach-container/postfach-container.component.html

...fach/postfach-container/postfach-container.component.scss

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

...stfach/postfach-container/postfach-container.component.ts

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

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