Add way to set timezone for DataSource and AbstractPropertySourceIterator

[Hanmac]

Feature Request

Extend AbstractPropertySourceIterator transformation from Datetime into String with option to set a different TimeZone instead.

Example, the Server is Running as UTC, but the AdminUser wants a different one (provided by TimezoneDetectorInterface)

The Datetime fields in the Admin are transformed into the right timezone by the Detector.

But exporting the Table with exporter caused it to be UTC again, which confused the User.

The problem is that DataSource is final, and when I try to decorate it, the Columns are already translated. (so it is difficult to interact with them)

Maybe related to #649

[VincentLanglet]

Maybe a good solution would be to allow extra option in

DataSource::createIterator

https://github.com/sonata-project/SonataDoctrineORMAdminBundle/blob/4.x/src/Exporter/DataSource.php#L24

public function createIterator(BaseProxyQueryInterface $query, array $fields, array $options = []): \Iterator

If you want to work on a PR.

[Hanmac]

i might look into it next week

i wonder if i can add a flag to disable the translation of the column keys for my other idea:
#649 (comment)

might be interesting if i could utilize Serializer Attributes with normalize the Data, or if that would be too much overhead