Add firstOrNew, firstOrCreate, and updateOrCreate methods

[hipsterjazzbo]

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This is a borderline necromantic resurrection of #179, because I need to use these methods :)

[hipsterjazzbo]

Not entirely sure why Travis is complaining about the missing sniffs. Any ideas?

[scrutinizer-notifier]

The inspection completed: 3 updated code elements

[nelson6e65]

Hi, @hipsterjazzbo Thanks for your contribution.

I still want this, but as it has some changes in PHP type-hints and Laravel helpers that may break v6 for some older PHP/Laravel versions, it will be left for v7 release. That release will, initially, remove compatibility with PHP < 7.4 and older Laravel versions. Then, v8 will remove compatibility to unsupported Laravel/PHP versions (PHP <=8.1, Laravel < 9 at this time).