feat(editor): Show avatars for users currently working on the same workflow (#7763)

This PR introduces the following changes:
- New Vue stores: `collaborationStore` and `pushConnectionStore`
- Front-end push connection handling overhaul: Keep only a singe
connection open and handle it from the new store
- Add user avatars in the editor header when there are multiple users
working on the same workflow
- Sending a heartbeat event to back-end service periodically to confirm
user is still active

- Back-end overhauls (authored by @tomi):
  - Implementing a cleanup procedure that removes inactive users
  - Refactoring collaboration service current implementation

---------

Co-authored-by: Tomi Turtiainen <10324676+tomi@users.noreply.github.com>

packages/cli/src/Server.ts

@@ -116,6 +116,7 @@ import { UserService } from './services/user.service';
 import { OrchestrationController } from './controllers/orchestration.controller';
 import { WorkflowHistoryController } from './workflows/workflowHistory/workflowHistory.controller.ee';
 import { InvitationController } from './controllers/invitation.controller';
+import { CollaborationService } from './collaboration/collaboration.service';
 
 const exec = promisify(callbackExec);
 
@@ -138,6 +139,8 @@ export class Server extends AbstractServer {
 
 	private postHog: PostHogClient;
 
+	private collaborationService: CollaborationService;
+
 	constructor() {
 		super('main');
 
@@ -233,6 +236,7 @@ export class Server extends AbstractServer {
 			.then(async (workflow) =>
 				Container.get(InternalHooks).onServerStarted(diagnosticInfo, workflow?.createdAt),
 			);
+		this.collaborationService = Container.get(CollaborationService);
 	}
 
 	private async registerControllers(ignoredEndpoints: Readonly<string[]>) {