updateEmail method
updates the email from a user in the users services and returns Future<http.Response>
Implementation
Future<http.Response> updateEmail(String email, String newEmail, jwt) {
var url = wsURL + 'update/email';
return http.put(Uri.parse(url),
headers: {HttpHeaders.authorizationHeader: 'Bearer ' + jwt},
body: {'email': email, 'newEmail': newEmail});
}