feat(handlers): replace 1s hack with rate-based delay for bulk send

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: AchoArnold

api/pkg/handlers/message_handler.go

@@ -161,11 +161,6 @@ func (h *MessageHandler) BulkSend(c *fiber.Ctx) error {
 		wg.Add(1)
 		go func(message services.MessageSendParams, index int) {
 			count.Add(1)
-			if message.SendAt == nil {
-				sentAt := time.Now().UTC().Add(time.Duration(index) * time.Second)
-				message.SendAt = &sentAt
-			}
-
 			response, err := h.service.SendMessage(ctx, message)
 			if err != nil {
 				count.Add(-1)

api/pkg/requests/message_bulk_send_request.go

@@ -54,7 +54,6 @@ func (input *MessageBulkSend) ToMessageSendParams(userID entities.UserID, source
 
 	var result []services.MessageSendParams
 	for index, to := range input.To {
-		sendAt := time.Now().UTC().Add(time.Duration(index) * time.Second)
 		result = append(result, services.MessageSendParams{
 			Source:            source,
 			Owner:             from,
@@ -63,9 +62,9 @@ func (input *MessageBulkSend) ToMessageSendParams(userID entities.UserID, source
 			UserID:            userID,
 			RequestReceivedAt: time.Now().UTC(),
 			Contact:           to,
-			SendAt:            &sendAt,
 			Content:           input.Content,
 			Attachments:       input.Attachments,
+			Index:             index,
 		})
 	}