feat(core): Replace client-oauth2 with an in-repo package (#6056)

Co-authored-by: Marcus <marcus@n8n.io>

packages/@n8n/client-oauth2/src/utils.ts

@@ -0,0 +1,83 @@
+/* eslint-disable @typescript-eslint/no-unsafe-member-access */
+/* eslint-disable @typescript-eslint/restrict-plus-operands */
+/* eslint-disable @typescript-eslint/no-unsafe-assignment */
+/* eslint-disable @typescript-eslint/no-explicit-any */
+import type { ClientOAuth2RequestObject } from './ClientOAuth2';
+import { ERROR_RESPONSES } from './constants';
+
+/**
+ * Check if properties exist on an object and throw when they aren't.
+ */
+export function expects(obj: any, ...args: any[]) {
+	for (let i = 1; i < args.length; i++) {
+		const prop = args[i];
+		if (obj[prop] === null) {
+			throw new TypeError('Expected "' + prop + '" to exist');
+		}
+	}
+}
+
+export class AuthError extends Error {
+	constructor(message: string, readonly body: any, readonly code = 'EAUTH') {
+		super(message);
+	}
+}
+
+/**
+ * Pull an authentication error from the response data.
+ */
+export function getAuthError(body: {
+	error: string;
+	error_description?: string;
+}): Error | undefined {
+	const message: string | undefined =
+		ERROR_RESPONSES[body.error] ?? body.error_description ?? body.error;
+
+	if (message) {
+		return new AuthError(message, body);
+	}
+
+	return undefined;
+}
+
+/**
+ * Ensure a value is a string.
+ */
+function toString(str: string | null | undefined) {
+	return str === null ? '' : String(str);
+}
+
+/**
+ * Sanitize the scopes option to be a string.
+ */
+export function sanitizeScope(scopes: string[] | string): string {
+	return Array.isArray(scopes) ? scopes.join(' ') : toString(scopes);
+}
+
+/**
+ * Create basic auth header.
+ */
+export function auth(username: string, password: string): string {
+	return 'Basic ' + Buffer.from(toString(username) + ':' + toString(password)).toString('base64');
+}
+
+/**
+ * Merge request options from an options object.
+ */
+export function getRequestOptions(
+	{ url, method, body, query, headers }: ClientOAuth2RequestObject,
+	options: any,
+): ClientOAuth2RequestObject {
+	const rOptions = {
+		url,
+		method,
+		body: { ...body, ...options.body },
+		query: { ...query, ...options.query },
+		headers: { ...headers, ...options.headers },
+	};
+	// if request authorization was overridden delete it from header
+	if (rOptions.headers.Authorization === '') {
+		delete rOptions.headers.Authorization;
+	}
+	return rOptions;
+}