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/test/unit/collaboration/collaboration.state.test.ts

@@ -0,0 +1,61 @@
+import { TIME } from '@/constants';
+import { CollaborationState } from '@/collaboration/collaboration.state';
+
+const origDate = global.Date;
+
+const mockDateFactory = (currentDate: string) => {
+	return class CustomDate extends origDate {
+		constructor() {
+			super(currentDate);
+		}
+	} as DateConstructor;
+};
+
+describe('CollaborationState', () => {
+	let collaborationState: CollaborationState;
+
+	beforeEach(() => {
+		collaborationState = new CollaborationState();
+	});
+
+	describe('cleanInactiveUsers', () => {
+		const workflowId = 'workflow';
+
+		it('should remove inactive users', () => {
+			// Setup
+			global.Date = mockDateFactory('2023-01-01T00:00:00.000Z');
+			collaborationState.addActiveWorkflowUser(workflowId, 'inactiveUser');
+
+			global.Date = mockDateFactory('2023-01-01T00:30:00.000Z');
+			collaborationState.addActiveWorkflowUser(workflowId, 'activeUser');
+
+			// Act: Clean inactive users
+			jest
+				.spyOn(global.Date, 'now')
+				.mockReturnValue(new origDate('2023-01-01T00:35:00.000Z').getTime());
+			collaborationState.cleanInactiveUsers(workflowId, 10 * TIME.MINUTE);
+
+			// Assert: The inactive user should be removed
+			expect(collaborationState.getActiveWorkflowUsers(workflowId)).toEqual([
+				{ userId: 'activeUser', lastSeen: new origDate('2023-01-01T00:30:00.000Z') },
+			]);
+		});
+
+		it('should not remove active users', () => {
+			// Setup: Add an active user to the state
+			global.Date = mockDateFactory('2023-01-01T00:30:00.000Z');
+			collaborationState.addActiveWorkflowUser(workflowId, 'activeUser');
+
+			// Act: Clean inactive users
+			jest
+				.spyOn(global.Date, 'now')
+				.mockReturnValue(new origDate('2023-01-01T00:35:00.000Z').getTime());
+			collaborationState.cleanInactiveUsers(workflowId, 10 * TIME.MINUTE);
+
+			// Assert: The active user should still be present
+			expect(collaborationState.getActiveWorkflowUsers(workflowId)).toEqual([
+				{ userId: 'activeUser', lastSeen: new origDate('2023-01-01T00:30:00.000Z') },
+			]);
+		});
+	});
+});