people: Add `make_user` helper function.

Made this function to avoid having incomplete `people` objects floating
around resulting in better type safety when using TypeScript. This function
has three required parameters - `user_id`, `email` and `full_name` and adds
default values to all other required properties.

web/src/people.js

@@ -1285,6 +1285,47 @@ export function report_late_add(user_id, email) {
     }
 }
 
+function make_user(user_id, email, full_name) {
+    // Used to create fake user objects for users who we see via some
+    // API call, such as fetching a message sent by the user, before
+    // we receive a full user object for the user via the events
+    // system.
+    //
+    // This function is an ugly hack in that it makes up a lot of
+    // values, but usually thesefake user objects only persist for
+    // less than a second before being replaced by a real user when
+    // the events system receives the user-created event for the new
+    // or newly visible user.
+    return {
+        user_id,
+        email,
+        full_name,
+        role: settings_config.user_role_values.member.code,
+        is_active: true,
+        is_admin: false,
+        is_owner: false,
+        is_guest: false,
+        is_bot: false,
+        is_moderator: false,
+        is_billing_admin: false,
+        // We explicitly don't set `avatar_url` for fake person objects so that fallback code
+        // will ask the server or compute a gravatar URL only once we need the avatar URL,
+        // it's important for performance that we not hash every user's email to get gravatar URLs.
+        avatar_url: undefined,
+        avatar_version: 0,
+        timezone: "",
+        date_joined: "",
+        delivery_email: null,
+        profile_data: {},
+        bot_owner_id: undefined,
+        bot_type: null,
+
+        // This property allows us to distinguish actual server person
+        // objects from fake person objects generated by this function.
+        is_missing_server_data: true,
+    };
+}
+
 function get_involved_people(message) {
     let involved_people;
 
@@ -1327,13 +1368,7 @@ export function extract_people_from_message(message) {
 
         report_late_add(user_id, person.email);
 
-        _add_user({
-            email: person.email,
-            user_id,
-            full_name: person.full_name,
-            is_admin: person.is_realm_admin || false,
-            is_bot: person.is_bot || false,
-        });
+        _add_user(make_user(user_id, person.email, person.full_name));
     }
 }
 

web/src/popovers.js

@@ -243,7 +243,10 @@ function render_user_info_popover(
     const show_manage_menu = !spectator_view && !is_me;
 
     let date_joined;
-    if (spectator_view) {
+
+    // Some users might not have `date_joined` field because of the missing server data.
+    // These users are added late in `people.js` via `extract_people_from_message`.
+    if (spectator_view && !user.is_missing_server_data) {
         date_joined = timerender.get_localized_date_or_time_for_format(
             parseISO(user.date_joined),
             "dayofyear_year",