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/support/index.js

@@ -18,3 +18,10 @@ import "./commands"
 
 // Alternatively you can use CommonJS syntax:
 // require('./commands')
+
+
+// Remove fetch, so Cypress can intercept XHRs
+// see https://github.com/cypress-io/cypress/issues/95
+Cypress.on("window:before:load", win => {
+  win.fetch = null
+})