improve: OAuth2 UI and test suite (via #5066)

* create `features` folder

* add base oauth2 server

* continue implementing OAuth tests

* WIP

* add password flow tests

* modify Password flow credential types

* remove query string credential type

* add test case for Authorization flow

* add specific Authorization value for Password flow test

* WIP

* fix linter issues

test/e2e-cypress/.eslintrc

@@ -0,0 +1,8 @@
+globals:
+  cy: false
+  Cypress: false
+  expect: false
+  assert: false
+
+rules:
+  "no-console": 0