Get rid of Class variable storage and move to instance storage

I'm building an admin/monitoring server that handles requests from both out production and qa Shopify store.
In the current setup, the user/password/site_uri are stored at the class level, so I can't create a prod session and a qa session and store them in memory.
For every request to the REST server I have to clear the current class variables and set for requested environment.

Additionally, this is not thread safe. If two REST requests arrive at the same time for different endpoints, they will clobber each other.

首先跟踪 user、password 和 site_uri 在哪里存储，以及 REST 请求如何访问它们，然后检查如何为不同的 Shopify 环境创建和选择 session。完成的标准是 production 和 QA session 可以在内存中共存，并且并发请求不再相互覆盖配置；为这两种情况添加或运行 coverage。