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

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

packages/@n8n/client-oauth2/.eslintrc.js

@@ -0,0 +1,14 @@
+const { sharedOptions } = require('@n8n_io/eslint-config/shared');
+
+/**
+ * @type {import('@types/eslint').ESLint.ConfigData}
+ */
+module.exports = {
+	extends: ['@n8n_io/eslint-config/base'],
+
+	...sharedOptions(__dirname),
+
+	rules: {
+		'@typescript-eslint/consistent-type-imports': 'error',
+	},
+};