LTI 1.3 Client Assertion to Access Token

[PhillipJacobs]

Hello,
Posting for one of our developers while we get her own account setup.

We are implementing LTI 1.3 and sucessfully getting id_token from url - https://sso.canvaslms.com/api/lti/authorize_redirect.

After verifying it with public JWK, how do we generate the client_assertion for getting access_token - /login/oauth2/token ?

{
"iss": "https://www.my-tool.com",
"sub": "<client_id>",
"aud": "https://<canvas_domain>/login/oauth2/token",
"iat": 1561750031,
"exp": 1561750631,
"jti": "dffdbdce-a9f1-427b-8fca-604182198783"
}

I went through the document and found how it look like, but not sure about "jti" value. Is there a reference document for verifying public JWK and getting client_assertion that we could look at?

Thank You,
-Phil