[MM-22648] basic auth external sites (#1295)

* fix not using babel

* wip

* added tests, moved to map, polifill-like to convert between object and map

* basic structure setup

* working, found new bug

* change buttons

* fix login issue

* remove logging code

* address CR comments

* remove custom function in favor of airbnb shim

* fix linting

* fix PM requested changes

* [MM-25323] fix basic auth cancelling

* fix crash when multiple request were made

* address UX comments, added external link for user
convenience

package.json

@@ -41,7 +41,7 @@
   "devDependencies": {
     "7zip-bin": "^4.1.0",
     "@babel/core": "^7.2.0",
-    "@babel/plugin-proposal-class-properties": "^7.2.0",
+    "@babel/plugin-proposal-class-properties": "^7.8.3",
     "@babel/plugin-proposal-object-rest-spread": "^7.2.0",
     "@babel/preset-env": "^7.2.0",
     "@babel/preset-react": "^7.0.0",
@@ -59,11 +59,11 @@
     "electron-connect": "^0.6.3",
     "electron-notarize": "^0.1.1",
     "eslint": "^6.6.0",
-    "eslint-plugin-mattermost": "github:mattermost/eslint-plugin-mattermost#070ce792d105482ffb2b27cfc0b7e78b3d20acee",
     "eslint-plugin-cypress": "^2.7.0",
     "eslint-plugin-eslint-comments": "^3.1.2",
     "eslint-plugin-header": "^3.0.0",
     "eslint-plugin-import": "^2.18.2",
+    "eslint-plugin-mattermost": "github:mattermost/eslint-plugin-mattermost#070ce792d105482ffb2b27cfc0b7e78b3d20acee",
     "eslint-plugin-react": "^7.16.0",
     "file-loader": "^2.0.0",
     "image-webpack-loader": "5.0.0",