Invalid [app] capability

Error Description
The capability you have entered to upload the app is invalid. Please enter the valid "app" capability.

Solution
REST API for the uploading the app on BrowserStack is:
curl -u "<username>:<accesskey>" -X POST "https://api-cloud.browserstack.com/app-automate/upload" -F "file=@/path/to/app/file/Application-debug.apk" -F 'data={"custom_id": "MyApp"}'

Note: custom_id is optional
The response of the app upload is
"app_url" : "bs://<hashed-id>"
Use the app_url value and set it in the app capability in your test code as:
caps['app'] = 'bs://<hashed-id>'

Note: The app capability also accepts the custom_id defined by you to upload an app
For more info, you may refer to our capabilities-list documentation
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