Custom Tools / SDK: Allow specifying an offline help URL

[mkhtran]

When the user has no internet connection or when the Help > Source setting is set to "Offline", clicking on a custom tool's help icon will always navigate to

• [AlteryxInstallDirectory]/bin/RuntimeData/HtmlAssets/help.alteryx.com/AlteryxCurrent/en/[helpURL]

which is practically never desirable for custom tools.

Specifying an offline help URL

Developers should have a way to (optionally) specify an offline help URL. This configuration could behave the same as `help_url` which already supports specifying both URLs and local files. If the offline help URL is not set, it would fallback to the `help_url` configuration.

{
  "tools": {
    "MyCustomTool": {
      "configuration": {
        "help_url": "https://mywebsite.com/help/my-custom-tool",
        "offline_help_url": "file://help/my-custom-tool.html"
      }
    }
  }
}