Missing claim for ngx.ctx.authenticated_consumer

[arwineap]

It is more important to sign the data that kong has derived, and therefore is the authoritative source for; than signing the untrusted data that was passed into the http request. Additionally, it seems like ngx.ctx.authenticated_consumer was intended to be used, as it's specified here:
https://github.com/Optum/kong-upstream-jwt/blob/master/src/handler.lua#L9

Would you support a PR that added a config to enable ngx.ctx.authenticated_consumer to be added as a claim in the jwt?

Alternatively, a more generic solution may be to allow users to configure a set of headers to be added to claims, some previous discussion here:
#15
#16

Would you support a PR that implemented an optional additional_header_claims config that allowed custom headers to be added?

Let me know what you think, I would love to help support