1. required_with:foo,bar,...
Use Case: The field under validation must be present and not empty only if any
========= of the other specified fields are present.
2. required_with_all:foo,bar,...
Use Case: The field under validation must be present and not empty only if all
========= of the other specified fields are present.
3. required_without:foo,bar,...
Use Case: The field under validation must be present and not empty only when
======== any of the other specified fields are not present.
4. required_without_all:foo,bar,...
Use Case: The field under validation must be present and not empty only when
========= all of the other specified fields are not present.