[Autofill Assistant] Added payer_email to the proto for PaymentDetails.

This will allow scripters to use this info for more informative messages to the user, see b/120009771.

Bug: 806868
Change-Id: I5b4003961a13e19159313b65529d3c33f1cf1c41
Reviewed-on: https://chromium-review.googlesource.com/c/1354003Reviewed-by: Stephane Zermatten <szermatt@chromium.org>
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Cr-Commit-Position: refs/heads/master@{#612161}

components/autofill_assistant/browser/actions/get_payment_information_action.cc

@@ -123,6 +123,8 @@ void GetPaymentInformationAction::OnGetPaymentInformation(
     processed_action_proto_->mutable_payment_details()
         ->set_is_terms_and_conditions_accepted(
             payment_information->is_terms_and_conditions_accepted);
+    processed_action_proto_->mutable_payment_details()->set_payer_email(
+        payment_information->payer_email);
   }
 
   UpdateProcessedAction(succeed ? ACTION_APPLIED : PAYMENT_REQUEST_ERROR);

components/autofill_assistant/browser/service.proto

@@ -272,6 +272,8 @@ message PaymentDetails {
   optional string card_issuer_network = 1;
   // Whether the integrated terms and conditions approval checkbox was checked.
   optional bool is_terms_and_conditions_accepted = 2;
+  // The email address of the payer.
+  optional string payer_email = 3;
 }
 
 message ProcessedActionProto {