server_events_dispatch: Handle "realm_user/remove" event.

This commit adds code to handle "realm_user/remove" event which
is received when a guest loses access to a user.

web/src/people.ts

@@ -1408,6 +1408,16 @@ export function deactivate(person: User): void {
     non_active_user_dict.set(person.user_id, person);
 }
 
+export function remove_inaccessible_user(user_id: number): void {
+    // We do not track inaccessible users in active_user_dict.
+    active_user_dict.delete(user_id);
+
+    // Create unknown user object for the inaccessible user.
+    const email = "user" + user_id + "@" + page_params.realm_bot_domain;
+    const unknown_user = make_user(user_id, email, INACCESSIBLE_USER_NAME);
+    _add_user(unknown_user);
+}
+
 export function report_late_add(user_id: number, email: string): void {
     // If the events system is not running, then it is expected that
     // we will fetch messages from the server that were sent by users

web/src/server_events_dispatch.js

@@ -8,6 +8,7 @@ import * as audible_notifications from "./audible_notifications";
 import * as blueslip from "./blueslip";
 import * as bot_data from "./bot_data";
 import * as browser_history from "./browser_history";
+import {buddy_list} from "./buddy_list";
 import * as compose_call from "./compose_call";
 import * as compose_call_ui from "./compose_call_ui";
 import * as compose_pm_pill from "./compose_pm_pill";
@@ -471,6 +472,16 @@ export function dispatch_normal_event(event) {
                         settings_users.update_bot_data(event.person.user_id);
                     }
                     break;
+                case "remove": {
+                    const user_id = event.person.user_id;
+                    people.remove_inaccessible_user(user_id);
+                    buddy_list.maybe_remove_user_id({user_id});
+                    message_live_update.update_user_full_name(
+                        user_id,
+                        people.INACCESSIBLE_USER_NAME,
+                    );
+                    break;
+                }
                 default:
                     blueslip.error("Unexpected event type realm_user/" + event.op);
                     break;

web/tests/dispatch.test.js

@@ -736,6 +736,11 @@ run_test("realm_user", ({override}) => {
     assert.equal(update_bot_stub.num_calls, 1);
     args = update_bot_stub.get_args("update_user_id", "update_bot_data");
     assert_same(args.update_user_id, event.person.user_id);
+
+    event = event_fixtures.realm_user__remove;
+    dispatch(event);
+    const removed_person = people.get_by_user_id(event.person.user_id);
+    assert.equal(removed_person.full_name, "translated: Unknown user");
 });
 
 run_test("restart", ({override}) => {

web/tests/lib/events.js

@@ -563,6 +563,15 @@ exports.fixtures = {
         },
     },
 
+    realm_user__remove: {
+        type: "realm_user",
+        op: "remove",
+        person: {
+            user_id: test_user.user_id,
+            full_name: "Unknown user",
+        },
+    },
+
     realm_user__update: {
         type: "realm_user",
         op: "update",