Update contracts to allow for UUID

[drbyte]

Must allow for string to $id parameter.

Also updated syntax to declare $guardName as nullable string.

/cc @erikn69

[erikn69]

Looks great to me,
it's a breaking change, but it's a major version, so 👍

#2089

Maybe change data type on findById is a breaking change for somebody overwriting that function,
if that is true, maybe for V6 release

[parallels999]

If you drop Php7.4 you could use Union Types on findbyId

[drbyte]

If you drop Php7.4 you could use Union Types on findbyId

Ya, I was itching for that too.

[parallels999]

Time to drop it

[drbyte]

Alright. Given that I'd like to avoid changing contracts again, if possible, using Union Types now saves that pain.