[8.x] Add ignoreTrashed to Unique validation rule

[PhiloNL]

Hi all!

I find myself adding whereNull('deleted_at') to the Rule::unique() quite often when working with models which can be soft deleted. This PR will add a simple helper to the unique validation rule.

Have a great day! 😄

// Before
[
  'email'=> [
    Rule::unique('users')->whereNull('deleted_at'),
  ],
];

// After
[
  'email'=> [
    Rule::unique('users')->ignoreTrashed(),
  ],
];

[rakibdevs]

What happens while restoring temporary deleted records? It could have possible duplicate entries.

[PhiloNL]

@rakibdevs this very much depends on your specific use case for using soft deletes. For example, I often use soft-deleted as a temporary backup. I prune all soft deleted models after a couple of days. So restoring models doesn't happen very often.

Alternatively, if you, for example, allow your users to restore data, I would implement a check to verify if the record is still unique. If the record is no longer unique, I will prompt the user to, e.g., change their username before restoring.