Laravel 10 compatibility

[alcaeus]

This PR replaces #2501 and adapts the library to accommodate the BC breaks introduced in Laravel 10.

The most impactful change is the handling of dates, which requires people to update their models to no longer use the $dates property, but instead define a cast for date fields in the $casts property (except for the created_at and updated_at fields).

Note that we will use this BC break as an opportunity to remove auto-casting for ObjectId and Binary instances, which has been previously planned for version 4.0 of this library. This will require people that want to use auto-casting for identifiers and binary fields to update the $casts property accordingly. Since this is a significant BC break (along with other BC breaks introduced by Laravel), we may decide to release Laravel 10 support in a new major version. This will not necessarily all of the changes previously prepared for 4.0 to accelerate the timeline for Laravel 10 support.

Any testing users can do with Laravel 10 to alert us to potential problems with this library are highly appreciated; we value your feedback to let us know what we need to fix or can improve.

[divine]

Honestly, we probably will need to separate each BC with a new PR.

[divine]

Hello,

Since this PR affects dates maybe it will make sense to merge this PR #2376 here as well?

Thanks!

[alcaeus]

I'm not familiar with that PR and will have to check that separately, but it isn't near the top of my list at the moment.