[v2 Route] Config Extension

[NeverBehave]

这个是v2 route延展部分，主要针对当前全局配置，并允许插件传递额外传递一些信息用于日后Core配套功能的整合

Layout

所有插件可以在目录声明config.js

module.export.prefix = "weibo";
module.export.env = ["app_key", "app_secret", "redirect_url"];
// When plugin loaded, core will parse this part into `${PREFIX}_${UPPER_CASE_ENV}` and look up in the dotenv
// If prefix not provided, default using directory

// This function will be called when any env listed was updated
module.export.load-config = function(env) {
   // Any pre-calculation steps, will be called each time when new value is set
    return {
          app_key: envs.app_keys,
          app_secret: envs.app_secret,
          redirect_url: envs.redirect_url,
          some_other_attrs: envs.app_keys + "random string"  // You may calculate your vars and use it later in the route
    }

   // You may also throw error at this stage, which mean if some vars is incorrect/missing, this plugin will not work and skip all together
}

module.export.meta = {
    puppeteer = true;
    override_ua = "This website require SAFARI..."
};

Life Cycle

在首次载入路由的时候，如果插件声明了config.js，则动态地载入并尝试初始化变量，config生成的结果将会在ctx.plugin.config传递给路由，子路由无需require('./config')，meta内容则会在ctx.plugin.meta中提供。如果load-config丢出错误，则直接终止路由载入，并提供错误信息

全局变量将会在ctx.global.config中暴露