fixes symfony#29030

fixes symfony#29030

fixes symfony#29030

fixes symfony#29030

…::denormalize (hultberg)

This PR was merged into the 4.4 branch.

Discussion
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[Serializer] Respect default context in DateTimeNormalizer::denormalize

| Q             | A
| ------------- | ---
| Branch?       | 4.4 <!-- see below -->
| Bug fix?      | yes
| New feature?  |no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #29030 <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | <!-- required for new features -->
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Hey there. 👋

I'm bringing my first code patch to symfony today and it's for fixing a bug I encountered today while working with DateTimeNormalizer. In my project I have set a default date format in the service container and I noticed that the denormalized date did not follow my set date format (I enforce time but the serialized date did not contain the time stamp which should have failed when using DateTime::createFromDate). After some debugging I discovered the issue described in issue #29030

`DateTimeNormalizer::normalize` respects the date time format in context or default context while `DateTimeNormalizer::denormalize` only respects the former. This patch adds logic to denormalize too attempt create a DateTime object from the default context format (by default set to `\DateTime::RFC3339`) with createFromFormat and then if that fails continue on with the current behaviour. In my opinion this patch does not break the symfony BC promise as it simply adds another way to denormalize the date time.

**One issue:** There are no error handling when creating the date time from default context as the logic just continues on which might give the impression to the developer that the denormalization with the specific format worked correctly. I was not able to find a way to handle any error and keeping BC.
**Future tough:** At some point the `new DateTime` call in denormalize should be deprecated since creating a date time with createFromFormat is considered "safer" in my eyes as it's very explicit while the call to `new DateTime` is implicit about the date format and must perform parsing and guessing of the intended format (explained over at https://www.php.net/manual/en/datetime.formats.php). Another thing about `new DateTime` is the terriable error handling as you must catch a `\Exception` which means you catch "what ever" exception that can exist, even `\ErrorException` since `\ErrorException extends \Exception`.

Fixes #29030
Alternative PR (closed) #33813

Commits
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763ea05 [Serializer] Respect default context in DateTimeNormalizer::denormalize