We're working on building the LTI Grades and Assignment integration and are currently optimizing it to work with Canvas.

We have everything working, but noticed that in the docs about the line item service we can provide an additional field that's not part of the LTI spec for submission type:

  "https://canvas.instructure.com/lti/submission_type": "{
  	"type":"external_tool",
  	"external_tool_url":"https://my.launch.url",
  }",

This is great and will make our integration significantly more powerful. However, our site can't be loaded in an iframe. Is there away to include a field on the submission type that indicates the link should be opened in a new window? We don't see any documentation anywhere to this effect.