Relay transactional email through Salesforce instead of SMTP (#9)

Reviewed-on: #9
Co-authored-by: Patrick Müller <patrick@mueller-patrick.tech>
Co-committed-by: Patrick Müller <patrick@mueller-patrick.tech>

src/models/tickets/tickets.interface.ts

@@ -109,6 +109,11 @@
  *         redeemedAt:
  *           type: string
  *           format: date-time
+ *         confirmationEmailStatus:
+ *           type: string
+ *           enum: [SENT, FAILED]
+ *           nullable: true
+ *           description: Outcome of the redemption confirmation email. null until the send resolves.
  *     VoucherCode:
  *       type: object
  *       required: [code, status, maxGuests, createdByEmail, createdAt, eligibleEventIds]
@@ -258,6 +263,8 @@ export interface RedemptionSummary {
 	guestCount: number;
 	guests: string[];
 	redeemedAt: Date;
+	// null until the post-redemption confirmation email send resolves.
+	confirmationEmailStatus: 'SENT' | 'FAILED' | null;
 }
 
 export interface VoucherCode {