[PROPOSAL] Add attributes metadata support

[Andrey Tsarev]

Please prefix your issue with one of the following: [BUG] [PROPOSAL] [QUESTION].

Package version, Laravel version

doctrine/orm:2.9.1
laravel-doctrine/orm: 1.7.7

Expected behaviour

Users must be able to specify the new attributes driver when using PHP 8+

Actual behaviour

There is no metadata driver in the package.

Steps to reproduce the behaviour

1. Create new Laravel project
2. Install laravel-doctrine/orm
3. Try to use #[ORM\Entity] and #[ORM\Table]
4. You get an error Class "....." is not a valid entity or mapped super class.

[Einar Gangsø]

Your PR have been released with 1.5.13, 1.6.7 and 1.7.9. Please try it out. Thanks 👍🏻

[Jurgen Bosch]

@eigan This does not seem to work with the migrations:diff command. Are you aware of that?