minor #21480 [Validator] UniqueEntity - add warning about not supported types and association mappings. (wkania)

This PR was merged into the 6.4 branch.

Discussion
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[Validator] UniqueEntity - add warning about not supported types and association mappings.

This constraint does not support Doctrine types such as ``simple_array``, ``json``, or ``jsonb``, nor does it handle association mappings like One-To-Many and Many-To-Many relationships. It may also not work correctly with custom Doctrine types. To perform uniqueness checks on such fields, you must define a custom repositoryMethod that implements the desired logic.

The previous [PR](#21262) closed itself due to an incorrect empty rebase, sorry.

Commits
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31ec2a0 [Validator] UniqueEntity - add warning about not supported types and association mappings.

Author: javiereguiluz

reference/constraints/UniqueEntity.rst

@@ -139,6 +139,14 @@ between all of the rows in your user table:
     that haven't been persisted as entities yet. You'll need to create your own
     validator to handle that case.
 
+.. warning::
+
+    This constraint does not support Doctrine types such as
+    ``simple_array``, ``json``, or ``jsonb``, nor does it handle association mappings
+    like ``OneToMany`` and ``ManyToMany`` relationships. It may also not work correctly
+    with custom Doctrine types. To perform uniqueness checks on such fields, you must
+    define a custom ``repositoryMethod`` that implements the desired logic.
+
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