Upgrade doctrine/dbal to 4 and doctrine/orm to 3

[arueckauer]

Earlier this month Doctrine ORM 3 and DBAL 4 were released.

The DBAL Upgrade to 4.0 document shows quite a few BC breaks. With also versions 2 and 3 supported, I supposed this could mean tedious upgrade work. Upon inspecting the usages of Doctrine\DBAL in the source, I noticed it mainly interacts with Doctrine\DBAL\Connection and very few other classes. If I am not mistaken, the upgrade could be easier than first expected. Maybe even allowing for ^2.12|^3.1|^4.0 (to be verified).

However, the required doctrine/orm version ^2.12 relies on doctrine/dbal version ^2.13.1 || ^3.2 and would need to be updated as well. Since there are deprecated versions of doctrine/orm being used, this will require some attention and work.

Before starting anything here, I would like to see, if there is a plan to support ORM 3 and DBAL 4 and if so, how this looks like. Would you like some help here? Looking forward to hearing from you. Thanks!