title: How can I override an array based setting from appsettings.json in an Environment variable?
body: <p>I have the following config in appsettings.json</p>
  
  <pre><code>"AvailableThemes": {
      "DefaultThemeKey": "abt",
      "Themes": [
        {
          "ThemeKey": "xc",
          "ThemeTitle": "XC 13"
        },
        {
          "ThemeKey": "abt",
          "ThemeTitle": "Taxis"
          "RegistrationSupported": true,
          "IntroText": "Hello",
        }
      ]
    }
  }
  </code></pre>
  
  <p>I need to be able to override RegistrationSupported in an environment variable so I can deploy the site with registration disabled and enable it when the linked site goes live.</p>
  
  <blockquote>
    <p>AvailableThemes:Themes:RegistrationSupported</p>
  </blockquote>
  
  <p>but that won't work because it won't know which item to override. I've tried an indexer like this...</p>
  
  <blockquote>
    <p>AvailableThemes:Themes[1]:RegistrationSupported</p>
  </blockquote>
  
  <p>...which didn't work.</p>