[IMP] mail: Move lastInterestDateTime to a getter

Part-of: odoo/odoo#115945

addons/mail/static/src/core/thread_model.js

@@ -85,6 +85,8 @@ export class Thread {
     suggestedRecipients = [];
     hasLoadingFailed = false;
     canPostOnReadonly;
+    /** @type {String} */
+    last_interest_dt;
 
     constructor(store, data) {
         Object.assign(this, {
@@ -387,6 +389,13 @@ export class Thread {
         return Object.values(this.rtcSessions).filter((session) => session.videoStream).length;
     }
 
+    get lastInterestDateTime() {
+        if (!this.last_interest_dt) {
+            return undefined;
+        }
+        return luxon.DateTime.fromISO(new Date(this.last_interest_dt).toISOString());
+    }
+
     /**
      *
      * @param {import("@mail/core/persona_model").Persona} persona

addons/mail/static/src/core/thread_service.js

@@ -481,17 +481,13 @@ export class ThreadService {
                 "name",
                 "state",
                 "group_based_subscription",
+                "last_interest_dt",
             ]);
             if (thread.model === "mail.channel" && serverData.channel) {
                 thread.channel = assignDefined(thread.channel ?? {}, serverData.channel);
             }
 
             thread.memberCount = serverData.channel?.memberCount ?? thread.memberCount;
-            if (serverData.last_interest_dt) {
-                thread.lastInterestDateTime = luxon.DateTime.fromISO(
-                    new Date(serverData.last_interest_dt).toISOString()
-                );
-            }
             if (serverData.channel && "serverMessageUnreadCounter" in serverData.channel) {
                 thread.serverMessageUnreadCounter = serverData.channel.serverMessageUnreadCounter;
             }