[Validator] Add docs for number constraint NegativeOrZero

Author: jschaedl

reference/constraints/NegativeOrZero.rst

@@ -0,0 +1,83 @@
+NegativeOrZero
+==============
+
+.. versionadded:: 4.3
+
+    The ``NegativeOrZero`` constraint was introduced in Symfony 4.3.
+
+Validates that a value is a negative number or equal to zero. To force that a value
+is only a negative number, see :doc:`/reference/constraints/Negative`.
+To force a value is positive or equal to zero,
+see :doc:`/reference/constraints/PositiveOrZero`.
+
+==========  ===================================================================
+Applies to  :ref:`property or method <validation-property-target>`
+Options     - `groups`_
+            - `message`_
+            - `payload`_
+Class       :class:`Symfony\\Component\\Validator\\Constraints\\NegativeOrZero`
+Validator   :class:`Symfony\\Component\\Validator\\Constraints\\LesserThanOrEqualValidator`
+==========  ===================================================================
+
+Basic Usage
+-----------
+
+The following constraint ensure that:
+
+* the ``withdraw`` of a  bankaccount ``TransferItem`` is a negative number or equal to zero
+
+.. configuration-block::
+
+    .. code-block:: php-annotations
+
+        // src/Entity/TransferItem.php
+        namespace App\Entity;
+
+        use Symfony\Component\Validator\Constraints as Assert;
+
+        class TransferItem
+        {
+            /**
+             * @Assert\NegativeOrZero
+             */
+            protected $withdraw;
+        }
+
+    .. code-block:: yaml
+
+        # config/validator/validation.yaml
+        App\Entity\TransferItem:
+            properties:
+                withdraw:
+                    - NegativeOrZero
+
+    .. code-block:: xml
+
+        <!-- config/validator/validation.xml -->
+        <?xml version="1.0" encoding="UTF-8" ?>
+        <constraint-mapping xmlns="http://symfony.com/schema/dic/constraint-mapping"
+            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xsi:schemaLocation="http://symfony.com/schema/dic/constraint-mapping https://symfony.com/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd">
+
+            <class name="App\Entity\TransferItem">
+                <property name="withdraw">
+                    <constraint name="NegativeOrZero"></constraint>
+                </property>
+            </class>
+        </constraint-mapping>
+
+    .. code-block:: php
+
+        // src/Entity/TransferItem.php
+        namespace App\Entity;
+
+        use Symfony\Component\Validator\Mapping\ClassMetadata;
+        use Symfony\Component\Validator\Constraints as Assert;
+
+        class TransferItem
+        {
+            public static function loadValidatorMetadata(ClassMetadata $metadata)
+            {
+                $metadata->addPropertyConstraint('withdraw', new Assert\NegativeOrZero();
+            }
+        }