fix: Update WhatsApp OTP template to single variable format (#974)

## Summary

- Fix Twilio error 21656 ("The ContentVariables you are using are not
valid") when sending WhatsApp OTP messages
- Update WhatsApp OTP template configuration to use single variable
format as required by Twilio/Meta's updated authentication template
requirements
- Modify validation logic to allow extra variables to be passed (and
ignored) for backward compatibility

## Background

Twilio/Meta updated their WhatsApp authentication template format.
Authentication templates now only accept a **single variable** (the OTP
code).

**Before:** `{"1":"123456","2":"MyOrg"}` ❌
**After:** `{"1":"123456"}` ✅

Reference: https://www.twilio.com/docs/content/whatsappauthentication

## Changes

- `internal/message/twilio_whatsapp_client.go`:
- Removed `TemplateVarOrgName` from `MessageTypeReceiverOTP`
configuration
- Updated `formatContentVariables` validation to check only for required
variables (extra variables are allowed but ignored)

- `internal/message/twilio_whatsapp_client_test.go`:
  - Updated test expectations for OTP formatting
  - Added test case for extra variables being allowed
  - Updated error message expectations

## Test plan
- [x] Unit tests pass (`go test ./internal/message/...`)
- [x] Integration test with real Twilio credentials - WhatsApp OTP
message sent successfully
- [X] Manual verification: OTP received on WhatsApp

Co-authored-by: Marwen Abid <[email protected]>

Author: wjuniorbh92

internal/message/twilio_whatsapp_client.go

@@ -83,7 +83,6 @@ var messageTemplateConfig = map[MessageType]templateMapping{
 	MessageTypeReceiverOTP: {
 		requiredVars: map[TemplateVariable]string{
 			TemplateVarReceiverOTP: "1",
-			TemplateVarOrgName:     "2",
 		},
 	},
 }
@@ -95,10 +94,11 @@ func formatContentVariables(messageType MessageType, vars map[TemplateVariable]s
 		return "", fmt.Errorf("unsupported message type %s for WhatsApp template variables", messageType)
 	}
 
-	// Validate all required variables are present
-	if len(vars) != len(config.requiredVars) {
-		return "", fmt.Errorf("expected %d template variables for message type %s, got %d",
-			len(config.requiredVars), messageType, len(vars))
+	// Validate all required variables are present (extra variables are allowed and ignored)
+	for templateVar := range config.requiredVars {
+		if _, ok := vars[templateVar]; !ok {
+			return "", fmt.Errorf("missing required template variable %s for message type %s", templateVar, messageType)
+		}
 	}
 
 	// Build content variables map with position mapping

internal/message/twilio_whatsapp_client_test.go

@@ -344,9 +344,9 @@ func Test_formatContentVariables(t *testing.T) {
 			messageType: MessageTypeReceiverOTP,
 			vars: map[TemplateVariable]string{
 				TemplateVarReceiverOTP: "123456",
-				TemplateVarOrgName:     "MyOrg",
+				TemplateVarOrgName:     "MyOrg", // extra variable is allowed but ignored
 			},
-			wantResult: `{"1":"123456","2":"MyOrg"}`,
+			wantResult: `{"1":"123456"}`,
 		},
 		{
 			name:        "unsupported message type",
@@ -362,17 +362,17 @@ func Test_formatContentVariables(t *testing.T) {
 			vars: map[TemplateVariable]string{
 				TemplateVarOrgName: "Test Organization",
 			},
-			wantErr: "expected 2 template variables for message type receiver_invitation, got 1",
+			wantErr: "missing required template variable registration_link for message type receiver_invitation",
 		},
 		{
-			name:        "too many variables for receiver OTP",
+			name:        "extra variables are allowed for receiver OTP",
 			messageType: MessageTypeReceiverOTP,
 			vars: map[TemplateVariable]string{
 				TemplateVarReceiverOTP: "123456",
 				TemplateVarOrgName:     "MyOrg",
 				TemplateVarFirstName:   "Extra",
 			},
-			wantErr: "expected 2 template variables for message type receiver_otp, got 3",
+			wantResult: `{"1":"123456"}`, // extra variables are ignored
 		},
 		{
 			name:        "incorrect variable for receiver invitation",
@@ -381,7 +381,7 @@ func Test_formatContentVariables(t *testing.T) {
 				TemplateVarOrgName:   "Test Organization",
 				TemplateVarFirstName: "Wrong Variable",
 			},
-			wantErr: "missing template variable registration_link for message type receiver_invitation",
+			wantErr: "missing required template variable registration_link for message type receiver_invitation",
 		},
 		{
 			name:        "incorrect variable for receiver OTP",
@@ -390,13 +390,13 @@ func Test_formatContentVariables(t *testing.T) {
 				TemplateVarFirstName: "Wrong Variable",
 				TemplateVarOrgName:   "MyOrg",
 			},
-			wantErr: "missing template variable receiver_otp for message type receiver_otp",
+			wantErr: "missing required template variable receiver_otp for message type receiver_otp",
 		},
 		{
 			name:        "empty variables map for receiver invitation",
 			messageType: MessageTypeReceiverInvitation,
 			vars:        map[TemplateVariable]string{},
-			wantErr:     "expected 2 template variables for message type receiver_invitation, got 0",
+			wantErr:     "missing required template variable",
 		},
 	}