chore: Add webhookUrl to Message model, DTOs, and services

Adds webhookUrl field to Message model, SendMessageDto, SendTemplateDto, SendContactDto, and related services to enable sending messages to a specified webhook URL. This change allows for more flexible message handling and delivery options.

Modified files:
- prisma/postgresql-schema.prisma
- src/api/dto/sendMessage.dto.ts
- src/api/services/channels/whatsapp.business.service.ts
- src/validate/message.schema.ts

Untracked files:
- prisma/migrations/20240723200254_add_webhookurl_on_message/

prisma/postgresql-schema.prisma

@@ -135,6 +135,7 @@ model Message {
   Media                        Media?
   OpenaiSession                OpenaiSession?  @relation(fields: [openaiSessionId], references: [id])
   openaiSessionId              String?
+  webhookUrl                   String?         @db.VarChar(500)
 }
 
 model MessageUpdate {