OZG-7000 feature toggle in navigation and pages

alfa-client/apps/admin/src/app/app.component.html

alfa-client/apps/admin/src/app/app.component.spec.ts

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

...t-form-page/organisationseinheit-form-page.component.html

...orm-page/organisationseinheit-form-page.component.spec.ts

...eit-form-page/organisationseinheit-form-page.component.ts

...ionseinheit-page/organisationseinheit-page.component.html

...seinheit-page/organisationseinheit-page.component.spec.ts

...ationseinheit-page/organisationseinheit-page.component.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

...es/users-roles/user-add-page/user-add-page.component.html

...users-roles/user-add-page/user-add-page.component.spec.ts

...ages/users-roles/user-add-page/user-add-page.component.ts

...sers-roles/user-roles-page/user-roles-page.component.html

...s-roles/user-roles-page/user-roles-page.component.spec.ts

.../users-roles/user-roles-page/user-roles-page.component.ts

...ient/libs/environment-shared/src/lib/environment.model.ts

alfa-client/libs/environment-shared/test/environment.ts