OZG-7510 extract mapping form; cleanup; adjust settings type model; move provider

alfa-client/apps/admin/src/main.ts

...ds-form-page/statistik-fields-form-page.component.spec.ts

...-fields-form-page/statistik-fields-form-page.component.ts

...ient/libs/admin/postfach-shared/src/lib/postfach.model.ts

...nt/libs/admin/postfach-shared/src/lib/postfach.service.ts

alfa-client/libs/admin/postfach-shared/src/test/postfach.ts

alfa-client/libs/admin/reporting-shared/src/index.ts

.../reporting-shared/src/lib/aggregation-mapping.provider.ts

...orting-shared/src/lib/aggregation-mapping.service.spec.ts

...t/libs/admin/reporting-shared/test/aggregation-mapping.ts

...dmin/settings-shared/src/lib/settings-resource.service.ts

...ient/libs/admin/settings-shared/src/lib/settings.model.ts

...nt/libs/admin/settings-shared/src/lib/settings.service.ts

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

...lient/libs/admin/settings-shared/src/lib/settings.util.ts

.../lib/admin-cancel-button/admin-cancel-button.component.ts

...lib/admin-save-button/admin-save-button.component.spec.ts

.../src/lib/admin-save-button/admin-save-button.component.ts

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

...ik-fields-form/admin-statistik-fields-form.component.html