doctrine/dbal 4 compatibility

• Bumped PHP requirement to 8.1 and added doctrine/dbal:4 compatibility to doctrine types

PHP 8.1 compatibility

• Added compatibility with php v8.1
• Added compatibility with doctrine/dbal v3
• Added compatibility with thecodingmachine/safe v2

PHP 8.0

• Bumped PHP requirement to 8.0 and added compatibility (thanks @goffyara)
• Migrated CI to Github Actions (and again thanks @goffyara)

PHP 7.4

• Bumped PHP requirement to 7.4
• Added typed properties for compatibiltiy with https://github.com/sspat/doctrine-nullable-embeddables

Added correct phpdoc typehint to named constructor

0.0.5

Added correct phpdoc typehint

Allowed Doctrine types to work with nullable values

0.0.4

Doctrine types can work with nullable values now

Fixed persistence error

0.0.3

Fixed missing properties during persistance of child classes

Fixed CI

0.0.2

Change PHP version for code style job in CI

First alpha release

0.0.1

Finished implementation