[REF] mail: have author in notification formatter

So that `Message.insert()` in JS becomes trivial, as it doesn't have
to infer the author of message to current user.

closes odoo/odoo#139501

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/models/mail_message.py

@@ -1135,6 +1135,7 @@ class Message(models.Model):
         the message was successfully sent or if an exception or bounce occurred.
         """
         return [{
+            'author': {'id': message.author_id.id, 'type': "partner"} if message.author_id else False,
             'id': message.id,
             'res_id': message.res_id,
             'model': message.model,

addons/mail/static/src/core/common/mail_core_common_service.js

@@ -49,13 +49,7 @@ export class MailCoreCommon {
                 }
             });
             this.busService.subscribe("mail.message/notification_update", (payload) => {
-                // implicit: failures are sent by the server at
-                // initialization only if the current partner is
-                // author of the message
-                this.store.Message.insert(
-                    payload.elements.map((data) => ({ ...data, author: this.store.self })),
-                    { html: true }
-                );
+                this.store.Message.insert(payload.elements, { html: true });
             });
             this.busService.subscribe("mail.message/toggle_star", (payload) => {
                 const { message_ids: messageIds, starred } = payload;

addons/mail/static/src/core/web/mail_core_web_service.js

@@ -21,13 +21,7 @@ export class MailCoreWeb {
     setup() {
         this.messagingService.isReady.then(() => {
             this.rpc("/mail/load_message_failures", {}, { silent: true }).then((messages) => {
-                // implicit: failures are sent by the server at
-                // initialization only if the current partner is
-                // author of the message
-                this.store.Message.insert(
-                    messages.map((m) => ({ ...m, author: this.store.user })),
-                    { html: true }
-                );
+                this.store.Message.insert(messages, { html: true });
                 this.store.failures.sort((f1, f2) => f2.lastMessage?.id - f1.lastMessage?.id);
             });
             this.busService.subscribe("mail.activity/updated", (payload) => {

addons/mail/static/tests/helpers/mock_server/models/mail_message.js

@@ -387,6 +387,7 @@ patch(MockServer.prototype, {
                 notifications.map((notification) => notification.id)
             );
             return {
+                author: message.author_id ? { id: message.author_id, type: "partner" } : false,
                 body: message.body,
                 date: message.date,
                 id: message.id,