feat: update verify_mail method to return boolean in email field and registration components

frontend/src/app/atomic/input/email-field/email-field.component.ts

@@ -28,7 +28,7 @@ export class EmailFieldComponent {
 
     @Output() valueChange = new EventEmitter<string>();
 
-    verify_mail() {
+    verify_mail(): boolean {
         return verify_email(this._value);
     }
 }

frontend/src/app/page/onboarding/registration/registration.component.ts

@@ -31,7 +31,7 @@ export class RegistrationComponent implements OnInit {
         }
     }
 
-    verify_mail() {
+    verify_mail(): boolean {
         return verify_email(this.mail);
     }