How does one add custom claims to the JWT issued by the OAuth flow?

How does one add custom claims to the JWT issued by an OAuth flow?

I'm trying to use FusionAuth to add claims required by Hasura.

In general you are going to want to use a Lambda to populate additional claims: https://fusionauth.io/docs/v1/tech/lambdas/jwt-populate

This issue has some notes about Hasura in particular: https://github.com/FusionAuth/fusionauth-issues/issues/61