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/helpers/oauth2-server/model.js

@@ -0,0 +1,141 @@
+// from https://github.com/pedroetb/node-oauth2-server-example
+
+var config = {
+  clients: [{
+    clientId: "application",
+    clientSecret: "secret"
+  }],
+  confidentialClients: [{
+    clientId: "confidentialApplication",
+    clientSecret: "topSecret"
+  }],
+  tokens: [],
+  users: [{
+    id: "123",
+    username: "swagger",
+    password: "password"
+  }]
+}
+
+/**
+ * Dump the memory storage content (for debug).
+ */
+
+var dump = function () {
+
+  console.log("clients", config.clients)
+  console.log("confidentialClients", config.confidentialClients)
+  console.log("tokens", config.tokens)
+  console.log("users", config.users)
+}
+
+/*
+ * Methods used by all grant types.
+ */
+
+var getAccessToken = function (bearerToken, callback) {
+
+  var tokens = config.tokens.filter(function (token) {
+
+    return token.accessToken === bearerToken
+  })
+
+  return callback(false, tokens[0])
+}
+
+var getClient = function (clientId, clientSecret, callback) {
+
+  var clients = config.clients.filter(function (client) {
+
+    return client.clientId === clientId && client.clientSecret === clientSecret
+  })
+
+  var confidentialClients = config.confidentialClients.filter(function (client) {
+
+    return client.clientId === clientId && client.clientSecret === clientSecret
+  })
+
+  callback(false, clients[0] || confidentialClients[0])
+}
+
+var grantTypeAllowed = function (clientId, grantType, callback) {
+
+  var clientsSource,
+    clients = []
+
+  if (grantType === "password") {
+    clientsSource = config.clients
+  } else if (grantType === "client_credentials") {
+    clientsSource = config.confidentialClients
+  }
+
+  if (clientsSource) {
+    clients = clientsSource.filter(function (client) {
+
+      return client.clientId === clientId
+    })
+  }
+
+  callback(false, clients.length)
+}
+
+var saveAccessToken = function (accessToken, clientId, expires, user, callback) {
+
+  config.tokens.push({
+    accessToken: accessToken,
+    expires: expires,
+    clientId: clientId,
+    user: user
+  })
+
+  callback(false)
+}
+
+/*
+ * Method used only by password grant type.
+ */
+
+var getUser = function (username, password, callback) {
+
+  var users = config.users.filter(function (user) {
+
+    return user.username === username && user.password === password
+  })
+
+  callback(false, users[0])
+}
+
+/*
+ * Method used only by client_credentials grant type.
+ */
+
+var getUserFromClient = function (clientId, clientSecret, callback) {
+
+  var clients = config.confidentialClients.filter(function (client) {
+
+    return client.clientId === clientId && client.clientSecret === clientSecret
+  })
+
+  var user
+
+  if (clients.length) {
+    user = {
+      username: clientId
+    }
+  }
+
+  callback(false, user)
+}
+
+/**
+ * Export model definition object.
+ */
+
+module.exports = {
+  getAccessToken: getAccessToken,
+  getClient: getClient,
+  grantTypeAllowed: grantTypeAllowed,
+  saveAccessToken: saveAccessToken,
+  getUser: getUser,
+  getUserFromClient: getUserFromClient
+}