Add client_id support for OpenID (#8579)

- One click OpenID authorization on Login page
- Add client_id help, config keys etc

Thanks to @egorkaru @ihostage for the
original work and testing.

browser/app/js/browser/OpenIDLoginButton.js

@@ -0,0 +1,57 @@
+/*
+ * MinIO Cloud Storage (C) 2019 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import React from "react"
+import { getRandomString } from "../utils"
+import storage from "local-storage-fallback"
+import { buildOpenIDAuthURL, OPEN_ID_NONCE_KEY } from './utils'
+
+export class OpenIDLoginButton extends React.Component {
+  constructor(props) {
+    super(props)
+    this.handleClick = this.handleClick.bind(this)
+  }
+
+  handleClick(event) {
+    event.stopPropagation()
+    const { authorizationEndpoint, clientId } = this.props
+
+    let redirectURI = window.location.href.split("#")[0]
+    if (redirectURI.endsWith('/')) {
+      redirectURI += 'openid'
+    } else {
+      redirectURI += '/openid'
+    }
+
+    // Store nonce in localstorage to check again after the redirect
+    const nonce = getRandomString(16)
+    storage.setItem(OPEN_ID_NONCE_KEY, nonce)
+
+    const authURL = buildOpenIDAuthURL(authorizationEndpoint, redirectURI, clientId, nonce)
+    window.location = authURL
+  }
+
+  render() {
+    const { children, className } = this.props
+    return (
+      <div onClick={this.handleClick} className={className}>
+        {children}
+      </div>
+    )
+  }
+}
+
+export default OpenIDLoginButton