Merge pull request #381 from IGNF/gpu-20422_unique_null

feat(core): unique constraint on nullable fields

Author: DD-Arras

validator-core/src/main/java/fr/ign/validator/database/internal/DuplicatedValuesFinder.java

@@ -51,6 +51,7 @@ public List<DuplicatedValue> findDuplicatedValues(Database database, String tabl
         RowIterator it = database.query(
             "SELECT " + columnName + " AS id, count(*) AS count"
                 + " FROM " + tableName
+                + " WHERE " + columnName + " IS NOT NULL"
                 + " GROUP BY " + columnName
                 + " HAVING count(*) > 1 ORDER BY count(*) DESC"
                 + " LIMIT " + LIMIT_PER_ATTRIBUTE