LTI 1.1 launch is not sending context_id (workshop instance id)

We use aXcelerate's LTI 1.1 integration to launch students into our external virtual classroom tool. When a student clicks the LTI link, aXcelerate sends us a signed launch request with a set of standard LTI parameters.

The problem: the launch is not including a context_id. We need context_id to be sent, and set to the aXcelerate workshop instance id that the student is launching from, so we know which workshop/class session to put them in.

Here is an example of what we currently receive on a launch (the important part is that there is no context_id field at all):

"ConsumerKey": "precise-17f90c8823d49076",
"MessageType": "basic-lti-launch-request",
"LtiVersion": "LTI-1p0",
"ResourceLinkId": "539710",
"ResourceLinkTitle": "TEST LTI Session #1",
"ResourceLinkDescription": null,
"UserId": "15219310",
"Roles": [
"Student"
],
"PersonNameFull": "Student 1",
"PersonNameGiven": "Student",
"PersonNameFamily": "1",
"PersonEmailPrimary": "student1@rosterme.au",
"ContextId": null,
"ContextLabel": null,
"ContextTitle": null,
"ToolConsumerInstanceGuid": null,
"ToolConsumerInstanceName": null,
"LaunchPresentationReturnUrl": null,
"LisOutcomeServiceUrl": null,
"LisResultSourcedId": null,
"Custom": {},
"RawParameters": {
"launch_presentation_document_target": "window",
"lis_person_contact_email_primary": "student1@rosterme.au",
"lis_person_name_family": "1",
"lis_person_name_full": "Student 1",
"lis_person_name_given": "Student",
"lti_message_type": "basic-lti-launch-request",
"lti_version": "LTI-1p0",
"oauth_consumer_key": "precise-17f90c8823d49076",
"oauth_nonce": "432612▇▇▇▇▇▇▇▇▇9289",
"oauth_signature": "/XbnyS9qPnsJyDa4GRDTZGztZI0=",
"oauth_signature_method": "HMAC-SHA1",
"oauth_timestamp": "1789603764",
"oauth_version": "1.0",
"resource_link_id": "539710",
"resource_link_title": "TEST LTI Session #1",
"roles": "Student",
"tool_consumer_info_product_family_code": "axcelerate",
"tool_consumer_info_version": "1.9",
"user_id": "15219310"

Our questions:

1) Can the LTI link be configured to send context_id, populated with the workshop instance id the student launched from?

2) If context_id can't carry the workshop instance id, can it be sent as an LTI custom parameter instead (for example custom_workshop_id = the workshop instance id)?

The goal is simply: on each launch, we need aXcelerate to tell us which workshop instance the student is launching from. Right now nothing in the launch identifies the workshop.