Fix mappings involving DateTimeInterface type

[priyadi]

A mapping from DateTimeInterface $timeCreated to DateTimeInterface $timeCreated will result in an error if the source variable is an instance of DateTimeImmutable:

DateTimeImmutable::createFromMutable(): Argument #1 ($object) must be of type DateTime, DateTimeImmutable given

This fixes the problem by using DateTimeImmutable::createFromInterface.

Also included complete permutations between all the possible DateTime types.

[Korbeil]

Thanks a lot for your first PR @priyadi 🎉
Could you fix CS ? You can run it locally by doing: tools/php-cs-fixer/vendor/bin/php-cs-fixer fix --config=tools/php-cs-fixer/.php-cs-fixer.php (You have to composer update inside tools/php-cs-fixer/ first)
Also, you will need to add a quick note about your changes into the CHANGELOG 🙏

[priyadi]

@Korbeil done

[Korbeil]

@Korbeil done

Could you also add a note in the CHANGELOG about your changes ? 🙏

[Korbeil]

Thanks a lot for your contribution ! ❤️