feat(core): Set up leader selection for multiple main instances (#7527)

https://linear.app/n8n/issue/PAY-933/set-up-leader-selection-for-multiple-main-instances

- [x] Set up new envs
- [x] Add config and license checks
- [x] Implement `MultiMainInstancePublisher`
- [x] Expand `RedisServicePubSubPublisher` to support
`MultiMainInstancePublisher`
- [x] Init `MultiMainInstancePublisher` on startup and destroy on
shutdown
- [x] Add to sandbox plans
- [x] Test manually

Note: This is only for setup - coordinating in reaction to leadership
changes will come in later PRs.

packages/cli/src/License.ts

@@ -23,6 +23,14 @@ type FeatureReturnType = Partial<
 	} & { [K in NumericLicenseFeature]: number } & { [K in BooleanLicenseFeature]: boolean }
 >;
 
+export class FeatureNotLicensedError extends Error {
+	constructor(feature: (typeof LICENSE_FEATURES)[keyof typeof LICENSE_FEATURES]) {
+		super(
+			`Your license does not allow for ${feature}. To enable ${feature}, please upgrade to a license that supports this feature.`,
+		);
+	}
+}
+
 @Service()
 export class License {
 	private manager: LicenseManager | undefined;
@@ -204,6 +212,10 @@ export class License {
 		return this.isFeatureEnabled(LICENSE_FEATURES.BINARY_DATA_S3);
 	}
 
+	isMultipleMainInstancesLicensed() {
+		return this.isFeatureEnabled(LICENSE_FEATURES.MULTIPLE_MAIN_INSTANCES);
+	}
+
 	isVariablesEnabled() {
 		return this.isFeatureEnabled(LICENSE_FEATURES.VARIABLES);
 	}