Add choices for transfer_type

sncfgtfs/models.py

@@ -39,6 +39,13 @@ class Direction(models.IntegerChoices):
     INBOUND = 1, _("Inbound")
 
 
+class TransferType(models.IntegerChoices):
+    RECOMMENDED = 0, _("Recommended")
+    TIMED = 1, _("Timed")
+    MINIMUM_TIME = 2, _("Minimum time")
+    NOT_POSSIBLE = 3, _("Not possible")
+
+
 class Agency(models.Model):
     agency_id = models.CharField(
         max_length=255,
@@ -420,6 +427,8 @@ class Transfer(models.Model):
 
     transfer_type = models.IntegerField(
         verbose_name=_("Transfer type"),
+        choices=TransferType,
+        default=TransferType.RECOMMENDED,
     )
 
     min_transfer_time = models.IntegerField(