Incomplete LTI launch

[JohnPa]

I keep track of incomplete LTI launches, and this one left me a bit puzzled:

{
	"oauth_consumer_key":"CONSUMER_KEY",
	"oauth_nonce":"A_RANDOM_ALPHA_STRING",
	"context_id":"A_RANDOM_ALPHA_STRING",
	"context_label":"EECS 183 WN 2019",
	"context_title":"EECS 183 WN 2019",
	"custom_canvas_course_id":"COURSE_ID",
	"custom_canvas_enrollment_state":"",
	"custom_canvas_user_id":"$Canvas.user.id",
	"custom_placement_id":"content:1",
	"ext_roles":"urn:lti:sysrole:ims\/lis\/None",
	"launch_presentation_document_target":"iframe",
	"launch_presentation_height":"400",
	"launch_presentation_locale":"en",
	"launch_presentation_return_url":"https:\/\/DOMAIN.instructure.com\/courses\/COURSE_ID\/external_content\/success\/external_tool_redirect",
	"launch_presentation_width":"800",
	"lis_person_contact_email_primary":"",
	"lti_message_type":"basic-lti-launch-request",
	"lti_version":"LTI-1p0",
	"resource_link_id":"content:1",
	"resource_link_title":"Lecture Recordings",
	"roles":"urn:lti:sysrole:ims\/lis\/None",
	"tool_consumer_info_product_family_code":"canvas",
	"tool_consumer_info_version":"cloud",
	"tool_consumer_instance_contact_email":"notifications@instructure.com",
	"tool_consumer_instance_guid":"A_RANDOM_ALPHA_STRING.DOMAIN.instructure.com",
	"tool_consumer_instance_name":"Institution name",
	"user_id":"",
	"expires":1755295686
}

 Does anyone know how these launch parameters could have been constructed? Test student accounts come through differently. The things that bug me:

1. It doesn't pass through user id (I don't actively use this, but it's been helpful in the past for troubleshooting)
2. Roles - very odd - "urn:lti:sysrole:ims\/lis\/None"

Any thoughts?