feat: add newsletter subscription from footer and registration

src/app/admin/admin.module.ts

...p/admin/components/delete-user/delete-user.component.scss

...app/admin/components/delete-user/delete-user.component.ts

...mponents/newsletter-users/newsletter-users.component.html

...nents/newsletter-users/newsletter-users.component.spec.ts

...components/newsletter-users/newsletter-users.component.ts

src/app/admin/components/panel/panel.component.html

src/app/admin/services/admin.service.ts

src/app/app-routing.module.ts

src/app/app.module.ts

src/app/footer/footer.component.html

src/app/form/form.component.html

src/app/form/form.component.ts

src/app/models/subscription-model.ts

...etter-subscription/newsletter-subscription.component.html

...etter-subscription/newsletter-subscription.component.scss

...er-subscription/newsletter-subscription.component.spec.ts

...sletter-subscription/newsletter-subscription.component.ts

src/app/services/newsletter.service.ts

src/app/shared/enum/adminPanel.enum.ts