Add BaseGraphqlService, support [github] V4 API (#3763)

* add base class for Graphql APIs
* add GithubAuthV4Service + updates to GH token pool
* update github forks to use GithubAuthV4Service
* rename GithubAuthService to GithubAuthV3Service

services/github/github-commit-status.service.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const Joi = require('@hapi/joi')
-const { GithubAuthService } = require('./github-auth-service')
+const { GithubAuthV3Service } = require('./github-auth-service')
 const { documentation, errorMessagesFor } = require('./github-helpers')
 const { NotFound, InvalidParameter } = require('..')
 
@@ -10,7 +10,7 @@ const schema = Joi.object({
   status: Joi.equal('identical', 'ahead', 'behind', 'diverged'),
 }).required()
 
-module.exports = class GithubCommitStatus extends GithubAuthService {
+module.exports = class GithubCommitStatus extends GithubAuthV3Service {
   static get category() {
     return 'issue-tracking'
   }