Update Entities to use Doctrine 2.6 types

[HeahDude]

Thanks to symfony/symfony#22689 Comment and Post entities should now use the new date time_immutable type for their $publishedAt property, so getters/setters should accept DateTimeInterface.

If you agree, this should be an easy pick.

[javiereguiluz]

It looks like a good idea! But let's not submit any pull request until #617 is merged. Thanks!

[voronkovich]

Also we should replace the json_array type by json because the json_array is deprecated since Doctrine 2.6.

[javiereguiluz]

This proposal is now unlocked and ready for someone who wants to contribute to this project with this easy pick. Thanks!

[gabel]

I guess datetime_immutable can not be applied as the \App\Controller\Admin\BlogController::newAction uses handle($request) which transforms the input into a \DateTime object and that would break the ORM mapping. Looks like this is related to symfony/symfony#19889.

If you need more details I can provide a PR with example implementation.

[gabel]

Talk is cheap.. PR is here #659 but test failing due to the mentioned issue.

[javiereguiluz]

Let's close this as "fixed". The JSON types are now used and the immutable date can't be used because of Symfony Forms. The related issue (symfony/symfony#9508) has been opened for more than 4 years, so this is more difficult to implement than it looks. Thanks!