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/requests.ts

@@ -4,6 +4,7 @@ import type {
 	IConnections,
 	ICredentialDataDecryptedObject,
 	ICredentialNodeAccess,
+	IDataObject,
 	INode,
 	INodeCredentialTestRequest,
 	IPinData,
@@ -14,7 +15,13 @@ import type {
 
 import { IsBoolean, IsEmail, IsOptional, IsString, Length } from 'class-validator';
 import { NoXss } from '@db/utils/customValidators';
-import type { PublicUser, IExecutionDeleteFilter, IWorkflowDb } from '@/Interfaces';
+import type {
+	PublicUser,
+	IExecutionDeleteFilter,
+	IWorkflowDb,
+	SecretsProvider,
+	SecretsProviderState,
+} from '@/Interfaces';
 import type { Role } from '@db/entities/Role';
 import type { User } from '@db/entities/User';
 import type { UserManagementMailer } from '@/UserManagement/email';
@@ -497,3 +504,25 @@ export declare namespace VariablesRequest {
 	type Update = AuthenticatedRequest<{ id: string }, {}, CreateUpdatePayload, {}>;
 	type Delete = Get;
 }
+
+export declare namespace ExternalSecretsRequest {
+	type GetProviderResponse = Pick<SecretsProvider, 'displayName' | 'name' | 'properties'> & {
+		icon: string;
+		connected: boolean;
+		connectedAt: Date | null;
+		state: SecretsProviderState;
+		data: IDataObject;
+	};
+
+	type GetProviders = AuthenticatedRequest;
+	type GetProvider = AuthenticatedRequest<{ provider: string }, GetProviderResponse>;
+	type SetProviderSettings = AuthenticatedRequest<{ provider: string }, {}, IDataObject>;
+	type TestProviderSettings = SetProviderSettings;
+	type SetProviderConnected = AuthenticatedRequest<
+		{ provider: string },
+		{},
+		{ connected: boolean }
+	>;
+
+	type UpdateProvider = AuthenticatedRequest<{ provider: string }>;
+}