feat: External Secrets storage for credentials (#6477)

Github issue / Community forum post (link here to close automatically):

---------

Co-authored-by: Romain Minaud <romain.minaud@gmail.com>
Co-authored-by: Valya Bullions <valya@n8n.io>
Co-authored-by: Csaba Tuncsik <csaba@n8n.io>
Co-authored-by: Giulio Andreini <g.andreini@gmail.com>
Co-authored-by: Omar Ajoue <krynble@gmail.com>

packages/cli/src/databases/repositories/settings.repository.ts

@@ -1,3 +1,4 @@
+import { EXTERNAL_SECRETS_DB_KEY } from '@/ExternalSecrets/constants';
 import { Service } from 'typedi';
 import { DataSource, Repository } from 'typeorm';
 import { ErrorReporterProxy as ErrorReporter } from 'n8n-workflow';
@@ -10,6 +11,21 @@ export class SettingsRepository extends Repository<Settings> {
 		super(Settings, dataSource.manager);
 	}
 
+	async getEncryptedSecretsProviderSettings(): Promise<string | null> {
+		return (await this.findOne({ where: { key: EXTERNAL_SECRETS_DB_KEY } }))?.value ?? null;
+	}
+
+	async saveEncryptedSecretsProviderSettings(data: string): Promise<void> {
+		await this.upsert(
+			{
+				key: EXTERNAL_SECRETS_DB_KEY,
+				value: data,
+				loadOnStartup: false,
+			},
+			['key'],
+		);
+	}
+
 	async dismissBanner({ bannerName }: { bannerName: string }): Promise<{ success: boolean }> {
 		const key = 'ui.banners.dismissed';
 		const dismissedBannersSetting = await this.findOneBy({ key });