feat: enable entering additional remarks in offer confirmation

src/Entity/Groups/AccommodationBooking.php

@@ -109,9 +109,15 @@ class AccommodationBooking implements BlameableEntityInterface, TimestampableEnt
     #[Assert\NotBlank(groups: ['edit'])]
     private ?string $lastName = null;
 
+    /**
+     * The `offer` group covers the one field a customer-facing booking cannot do without:
+     * the access link and every notification are addressed to it. It is enforced on
+     * creation as soon as the booking is not a draft, while `edit` additionally demands
+     * the rest of the contact data.
+     */
     #[ORM\Column(length: 255, nullable: true)]
-    #[Assert\NotBlank(groups: ['edit'])]
-    #[Assert\Email(groups: ['edit'])]
+    #[Assert\NotBlank(groups: ['edit', 'offer'])]
+    #[Assert\Email(groups: ['edit', 'offer'])]
     private ?string $email = null;
 
     #[ORM\Column(length: 50, nullable: true)]