Add custom arguments to the CastWith attribute

[xico42]

Custom arguments can be used to provide metadata and extra context for
the user-defined casters.

This can be used, for example, to create generic array casters.

Fixes #193

[jaulz]

@brendt any chance to merge this soon? 😊

It would be also cool if it could automatically pass the type from the comment (i.e. /** @var \Spatie\DataTransferObject\Tests\Foo[] */) but that's maybe a separate PR?

[brendt]

I'll try to look at it this week :)

[brendt]

I'm going to add a few more additions myself before tagging:

• I'm thinking of adding GenericArrayCaster to the package itself
• I'll spread the args again when passed to the caster

[brendt]

@fcoedno would you mind reviewing my commit? 0df542e

[aidan-casey]

@brendt - Is there any reason to not add a check for whether the type implements ArrayAccess in the GenericArrayCaster?

[xico42]

@brendt it looks great. Looking forward to seeing it in the next release.

[brendt]

@aidan-casey good question, I copied that part from the original PR… would you like to send a PR to improve it? Otherwise I'll try to look at it this week :)

[aidan-casey]

@brendt - I am happy to create a PR for it, just wasn't sure if it was something you purposely didn't want in the package.

I'll draft something up soon.