feat(core): Coordinate manual workflow activation and deactivation in multi-main scenario (#7643)

Followup to #7566 | Story: https://linear.app/n8n/issue/PAY-926

### Manual workflow activation and deactivation

In a multi-main scenario, if the user manually activates or deactivates
a workflow, the process (whether leader or follower) that handles the
PATCH request and updates its internal state should send a message into
the command channel, so that all other main processes update their
internal state accordingly:

- Add to `ActiveWorkflows` if activating
- Remove from `ActiveWorkflows` if deactivating
- Remove and re-add to `ActiveWorkflows` if the update did not change
activation status.

After updating their internal state, if activating or deactivating, the
recipient main processes should push a message to all connected
frontends so that these can update their stores and so reflect the value
in the UI.

### Workflow activation errors

On failure to activate a workflow, the main instance should record the
error in Redis - main instances should always pull activation errors
from Redis in a multi-main scenario.

### Leadership change

On leadership change...

- The old leader should stop pruning and the new leader should start
pruning.
- The old leader should remove trigger- and poller-based workflows and
the new leader should add them.

packages/cli/src/ActivationErrors.service.ts

@@ -0,0 +1,52 @@
+import { Service } from 'typedi';
+import { CacheService } from './services/cache.service';
+import { jsonParse } from 'n8n-workflow';
+
+type ActivationErrors = {
+	[workflowId: string]: string; // error message
+};
+
+@Service()
+export class ActivationErrorsService {
+	private readonly cacheKey = 'workflow-activation-errors';
+
+	constructor(private readonly cacheService: CacheService) {}
+
+	async set(workflowId: string, errorMessage: string) {
+		const errors = await this.getAll();
+
+		errors[workflowId] = errorMessage;
+
+		await this.cacheService.set(this.cacheKey, JSON.stringify(errors));
+	}
+
+	async unset(workflowId: string) {
+		const errors = await this.getAll();
+
+		if (Object.keys(errors).length === 0) return;
+
+		delete errors[workflowId];
+
+		await this.cacheService.set(this.cacheKey, JSON.stringify(errors));
+	}
+
+	async get(workflowId: string) {
+		const errors = await this.getAll();
+
+		if (Object.keys(errors).length === 0) return null;
+
+		return errors[workflowId];
+	}
+
+	async getAll() {
+		const errors = await this.cacheService.get<string>(this.cacheKey);
+
+		if (!errors) return {};
+
+		return jsonParse<ActivationErrors>(errors);
+	}
+
+	async clearAll() {
+		await this.cacheService.delete(this.cacheKey);
+	}
+}