…alues (dunglas)This PR was squashed before being merged into the 4.3-dev branch (closes#29641).Discussion----------[Validator] NotBlank: add a new option to allow null values| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | yes <!-- don't forget to update src/**/CHANGELOG.md files -->| BC breaks?    | no     <!-- seehttps://symfony.com/bc -->| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->| Fixed tickets |#27876| License       | MIT| Doc PR        | todoThis PR adds a new option to the `@NotBlank` constraint to allow null values. As described in#27876, this is particularly useful when creating web APIs.Commits-------484d22a [Validator] NotBlank: add a new option to allow null values

…aviereguiluz)This PR was merged into the master branch.Discussion----------Document the allowNull option for NotBlank constraintThis documentssymfony/symfony#29641Commits-------ab2c4f1 Document the allowNull option for NotBlank constraint

…reject empty strings (ogizanagi)This PR was merged into the 4.4 branch.Discussion----------[Validator] Add a Length::$allowEmptyString option to reject empty strings| Q             | A| ------------- | ---| Branch?       | 4.4 <!-- see below -->| Bug fix?      | no| New feature?  | yes <!-- please update src/**/CHANGELOG.md files -->| BC breaks?    | no     <!-- seehttps://symfony.com/bc -->| Deprecations? | yes <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->| Fixed tickets | N/A   <!-- #-prefixed issue number(s), if any -->| License       | MIT| Doc PR        | Todo (change the warning on top ofhttps://symfony.com/doc/current/reference/constraints/Length.html)which defaults to `true` in 4.4 but will trigger a deprecation if not set explicitlyin order to make the default `false` in 5.0.While it could be solved now thanks to#29641 by using both `@Length(min=1)` & `@NotBlank(allowNull=true)` constraints,as expressed in#27876 (comment) and following comments, the `@Length(min=1)` behavior doesn't match our expectations when reading it: it feels logical to invalidate empty strings, but it actually doesn't.Hence the proposal of making the behavior of rejecting empty strings the default in 5.0.In my opinion, the flag could even be removed later.Commits-------e113e7f [Validator] Add a Length::$allowEmptyString option to reject empty strings