We want to remove/refactor the whole ModelValidator class as part of the
Doctrine refactor.
This commit moves the method ModelValidator::validateNonRoleEmail() to a
new Validator class as the method is not used by the validator system of
the Paris models. ModelValidator::validateEmail() was also moved as it
is called by ModelValidator::validateNonRoleEmail().
[MAILPOET-4343]
Per WP security best practices, sanitization should be handled as early
as possible. So this commit move updates the calls to sanitize the
segment name and description to the part of the code where the user
input is first processed, instead of when the data is saved to the
database.
[MAILPOET-5232]
