feat: create Mailjet lists for travel mailings

src/Service/TravelIndex.php

@@ -127,6 +127,26 @@ class TravelIndex
         return $this->generateFilesMap()[$dateId]['label'] ?? null;
     }
 
+    /**
+     * Resolve a date code to the travel's start date.
+     *
+     * @param string $dateCode The date code to resolve
+     *
+     * @return \DateTimeImmutable|null The start date, or null if the code is not found or the travel has none
+     */
+    public function mapDateCodeToStartDate(string $dateCode): ?\DateTimeImmutable
+    {
+        $dateId = $this->mapDateCodeToId($dateCode);
+
+        if (null === $dateId) {
+            return null;
+        }
+
+        $dateFrom = $this->generateFilesMap()[$dateId]['dateFrom'] ?? null;
+
+        return $dateFrom instanceof \DateTimeImmutable ? $dateFrom : null;
+    }
+
     /**
      * Convert a hotel code string to its corresponding hotel ID.
      *