Feature: avoid duplicates for the same period in acc period user history

.changes/unreleased/Feature-20230627-151615.yaml

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+kind: Feature
+body: "Force accompanying period user history to be unique for the same period and
+  stardate/enddate [:warning: may encounter migration issue]"
+time: 2023-06-27T15:16:15.775571488+02:00
+custom:
+  Issue: ""
+  Long: "If some issue is encountered during migration, use this SQL to find the line which are in conflict, examine the problem and delete some of the concerning line
+
+    ```sql
+
+    -- to see the line which are in conflict with another one
+
+    SELECT o.*
+
+    FROM chill_person_accompanying_period_user_history o
+
+    JOIN chill_person_accompanying_period_user_history c ON o.id < c.id AND o.accompanyingperiod_id = c.accompanyingperiod_id
+
+    WHERE tsrange(o.startdate, o.enddate, '[)') && tsrange(c.startdate, c.enddate, '[)')
+
+    ORDER BY accompanyingperiod_id;
+
+    -- to examine line in conflict for a given accompanyingperiod_id (given by the previous query)
+
+    SELECT * FROM chill_person_accompanying_period_user_history WHERE accompanyingperiod_id = IIIIDDDD order by startdate, enddate;
+
+    ```
+    "

src/Bundle/ChillPersonBundle/migrations/Version20230627130331.php

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+<?php
+
+declare(strict_types=1);
+
+/*
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Chill\Migrations\Person;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20230627130331 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Add constraint to force unicity on chill_person_accompanying_period_user_history';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE chill_person_accompanying_period_user_history
+        ADD CONSTRAINT acc_period_user_history_not_overlaps
+        EXCLUDE USING GIST (accompanyingperiod_id with =, tsrange(startdate, enddate) with &&)
+        DEFERRABLE INITIALLY DEFERRED');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE chill_person_accompanying_period_user_history DROP CONSTRAINT acc_period_user_history_not_overlaps');
+    }
+}