redefine ENUMs with enumType about admin

[arhimede]

@kakapiciu will try to implement a proof of concept
solution 2, variant #2

[alexmerlin]

Solution 1: Mapping to Varchars is what we're currently using and as we know, it has it's own flaws (showing unnecessary modifications in each migration).

Solution 2: Defining a Type seems to be the preferred approach in most frameworks.
In addition to the method described in the article, there should be either:

1. An abstract type that then could be extended by each custom enumType

   abstract class AbstractEnumType extends Type containing all the methods defined in the article (getSQLDeclaration, convertToPHPValue etc)
   Then custom enumTypes extending AbstractEnumType that have only one purpose, providing the values (which can be defined as constants in the custom enumType and also used in the $values array - this way the values are defined only once and constants can also be reused outside the class)

2. One single enumType that when added to a property, can be configured (if needed, the values parameter's name can be changed to a more suitable one):

   #[ORM\Column(name: "status", type: EnumType::class, values: ["pending", "active"])]
   If this can be implemented, it would be the easisest solution both to write and to use.

Note:
Both solutions (the abstract / generic enumTypes) are theoretical, I did not try them in practice. Their purpose is only to give an idea on where to start implementing these types.