config API_TOKEN envs with customized name

[oliveagle]

Currently, there are numerous AI API providers, and many of them offer services following the OpenAI-compatible mode. In practical use, when tools in different scenarios need to call different models and models of varying sizes, the token names in the environment variables (env) often conflict.
For example,

• Tool A uses the OPENAI_API_KEY to call the GPT-40 model on OPENROUTER,
• while the Zed or another tool also intends to use the OPENAI_API_KEY to call the Deepseek-R1 model from another API provider.

At this time, the environment variable name of OPENAI_API_KEY creates a conflict.
Fortunately, most tools provide the function to configure the OPENAI_API_KEY. However, the Zed tool lacks this feature, which undoubtedly causes troubles for users. (If there is , plz let me know)

In order to give the Zed tool higher flexibility when using the services of other API providers, it is recommended that Zed can provide a function to customize the environment variable name of the OPENAI_API_KEY, or allow users to directly make relevant configurations in the configuration file. In this way, the inconvenience caused by the conflict of environment variable names can be effectively avoided, and the user experience can be improved.

e.g.:

// directly configired in config file
{
   "openai": {
        "api_key": "xxxxxx",
   }
}


or 

// provide env_name customizaition
{
       "openai" {
            "api_key_env_name":  "ZED_OPENAI_API_KEY"
      }
}

or  even

 defaultly, every env configurations are prefixed with 'ZED_xxxxx'