fix: show upgrade prompt when email transcript returns 402 (#13650)

- Show a specific upgrade prompt when free-plan users attempt to send an
email transcript and the API returns a 402 Payment Required error
- Previously, a generic "There was an error, please try again" message
was shown for all failures, including plan restrictions

Fixes
https://linear.app/chatwoot/issue/CW-6538/show-ui-feedback-for-email-transcript-402-plan-restriction

app/javascript/dashboard/components/widgets/conversation/EmailTranscriptModal.vue

@@ -85,7 +85,12 @@ export default {
         useAlert(this.$t('EMAIL_TRANSCRIPT.SEND_EMAIL_SUCCESS'));
         this.onCancel();
       } catch (error) {
-        useAlert(this.$t('EMAIL_TRANSCRIPT.SEND_EMAIL_ERROR'));
+        const status = error?.response?.status;
+        if (status === 402) {
+          useAlert(this.$t('EMAIL_TRANSCRIPT.SEND_EMAIL_PAYMENT_REQUIRED'));
+        } else {
+          useAlert(this.$t('EMAIL_TRANSCRIPT.SEND_EMAIL_ERROR'));
+        }
       } finally {
         this.isSubmitting = false;
       }

app/javascript/dashboard/i18n/locale/en/conversation.json

@@ -305,6 +305,7 @@
     "CANCEL": "Cancel",
     "SEND_EMAIL_SUCCESS": "The chat transcript was sent successfully",
     "SEND_EMAIL_ERROR": "There was an error, please try again",
+    "SEND_EMAIL_PAYMENT_REQUIRED": "Email transcript is not available on your current plan. Please upgrade to use this feature.",
     "FORM": {
       "SEND_TO_CONTACT": "Send the transcript to the customer",
       "SEND_TO_AGENT": "Send the transcript to the assigned agent",

app/javascript/dashboard/store/modules/conversations/actions.js

@@ -457,11 +457,7 @@ const actions = {
   },
 
   sendEmailTranscript: async (_, { conversationId, email }) => {
-    try {
-      await ConversationApi.sendEmailTranscript({ conversationId, email });
-    } catch (error) {
-      throw new Error(error);
-    }
+    await ConversationApi.sendEmailTranscript({ conversationId, email });
   },
 
   updateCustomAttributes: async (