refactor(core): Parse Webhook request bodies on-demand (#6394)

Also,
1. Consistent CORS support ~on all three webhook types~ waiting webhooks never supported CORS. I'll fix that in another PR
2. [Fixes binary-data handling when request body is text, json, or xml](https://linear.app/n8n/issue/NODE-505/webhook-binary-data-handling-fails-for-textplain-files).
3. Reduced number of middleware that each request has to go through.
4. Removed the need to maintain webhook endpoints in the auth-exception list.
5. Skip all middlewares (apart from `compression`) on Webhook routes. 
6. move `multipart/form-data` support out of individual nodes
7. upgrade `formidable`
8. fix the filenames on binary-data in webhooks nodes
9. add unit tests and integration tests for webhook request handling, and increase test coverage

packages/cli/test/unit/webhooks.test.ts

@@ -0,0 +1,76 @@
+import type { SuperAgentTest } from 'supertest';
+import { agent as testAgent } from 'supertest';
+import { mock } from 'jest-mock-extended';
+
+import config from '@/config';
+import { AbstractServer } from '@/AbstractServer';
+import { ActiveWorkflowRunner } from '@/ActiveWorkflowRunner';
+import { ExternalHooks } from '@/ExternalHooks';
+import { InternalHooks } from '@/InternalHooks';
+import { TestWebhooks } from '@/TestWebhooks';
+import { WaitingWebhooks } from '@/WaitingWebhooks';
+import type { IResponseCallbackData } from '@/Interfaces';
+
+import { mockInstance } from '../integration/shared/utils';
+
+let agent: SuperAgentTest;
+
+describe('WebhookServer', () => {
+	mockInstance(ExternalHooks);
+	mockInstance(InternalHooks);
+
+	describe('CORS', () => {
+		const corsOrigin = 'https://example.com';
+		const activeWorkflowRunner = mockInstance(ActiveWorkflowRunner);
+		const testWebhooks = mockInstance(TestWebhooks);
+		mockInstance(WaitingWebhooks);
+
+		beforeAll(async () => {
+			const server = new (class extends AbstractServer {
+				testWebhooksEnabled = true;
+			})();
+			await server.start();
+			agent = testAgent(server.app);
+		});
+
+		const tests = [
+			['webhook', activeWorkflowRunner],
+			['webhookTest', testWebhooks],
+			// TODO: enable webhookWaiting after CORS support is added
+			// ['webhookWaiting', waitingWebhooks],
+		] as const;
+
+		for (const [key, manager] of tests) {
+			describe(`for ${key}`, () => {
+				it('should handle preflight requests', async () => {
+					const pathPrefix = config.getEnv(`endpoints.${key}`);
+					manager.getWebhookMethods.mockResolvedValueOnce(['GET']);
+
+					const response = await agent.options(`/${pathPrefix}/abcd`).set('origin', corsOrigin);
+					expect(response.statusCode).toEqual(204);
+					expect(response.body).toEqual({});
+					expect(response.headers['access-control-allow-origin']).toEqual(corsOrigin);
+					expect(response.headers['access-control-allow-methods']).toEqual('OPTIONS, GET');
+				});
+
+				it('should handle regular requests', async () => {
+					const pathPrefix = config.getEnv(`endpoints.${key}`);
+					manager.getWebhookMethods.mockResolvedValueOnce(['GET']);
+					manager.executeWebhook.mockResolvedValueOnce(mockResponse({ test: true }));
+
+					const response = await agent.get(`/${pathPrefix}/abcd`).set('origin', corsOrigin);
+					expect(response.statusCode).toEqual(200);
+					expect(response.body).toEqual({ test: true });
+					expect(response.headers['access-control-allow-origin']).toEqual(corsOrigin);
+				});
+			});
+		}
+
+		const mockResponse = (data = {}, status = 200) => {
+			const response = mock<IResponseCallbackData>();
+			response.responseCode = status;
+			response.data = data;
+			return response;
+		};
+	});
+});