Add third-party self-referential relations

Introduce a self-referential many-to-many relation table so a
third party can have child third parties. Each relation is
directional (parent to child); both directions can coexist as
independent rows.

Add a first_level boolean on third_parties (default true) with
a filter on the list page that defaults to showing only
first-level third parties.

Frontend adds a "Third Parties" tab on the detail page where
users can link existing third parties or create new ones from
the common third party catalog (created as non-first-level).
The list page gets a First Level/All toggle filter.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

packages/n8n-node/nodes/Probo/actions/thirdParty/unlinkThirdParty.operation.ts

@@ -0,0 +1,70 @@
+// Copyright (c) 2025-2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+import type { INodeProperties, IExecuteFunctions, INodeExecutionData } from 'n8n-workflow';
+import { proboApiRequest } from '../../GenericFunctions';
+
+export const description: INodeProperties[] = [
+	{
+		displayName: 'Parent Third Party ID',
+		name: 'parentThirdPartyId',
+		type: 'string',
+		displayOptions: {
+			show: {
+				resource: ['thirdParty'],
+				operation: ['unlinkThirdParty'],
+			},
+		},
+		default: '',
+		description: 'The ID of the parent third party',
+		required: true,
+	},
+	{
+		displayName: 'Child Third Party ID',
+		name: 'childThirdPartyId',
+		type: 'string',
+		displayOptions: {
+			show: {
+				resource: ['thirdParty'],
+				operation: ['unlinkThirdParty'],
+			},
+		},
+		default: '',
+		description: 'The ID of the child third party to unlink',
+		required: true,
+	},
+];
+
+export async function execute(
+	this: IExecuteFunctions,
+	itemIndex: number,
+): Promise<INodeExecutionData> {
+	const parentThirdPartyId = this.getNodeParameter('parentThirdPartyId', itemIndex) as string;
+	const childThirdPartyId = this.getNodeParameter('childThirdPartyId', itemIndex) as string;
+
+	const query = `
+		mutation DeleteThirdPartyThirdPartyMapping($input: DeleteThirdPartyThirdPartyMappingInput!) {
+			deleteThirdPartyThirdPartyMapping(input: $input) {
+				removedThirdPartyId
+			}
+		}
+	`;
+
+	const responseData = await proboApiRequest.call(this, query, { input: { parentThirdPartyId, childThirdPartyId } });
+
+	return {
+		json: responseData,
+		pairedItem: { item: itemIndex },
+	};
+}