Include subject in required claims for client assertion

[stoivo]

Jeg hadde ikke med for det står at det ikke er påkreved

her er et eksempen på at det feiler

``` > POST https://test.idporten.no/token Content-Type: application/x-www-form-urlencoded Connection: close Host: test.idporten.no User-Agent: http.rb/5.1.1 client_id=f18991af-3ec9-4f93-963b-8ea4d04ee802&grant_type=authorization_code&code=euIXF4V808MGhkqAmd8jeQ.2-Nu-USujrqQvZd7ilTszA&redirect_uri=http%3A%2F%2Flocalhost%3A3500%2Fsession%2Ftoken&code_verifier=t07EPrMzAxzZw3ArD71oqxGKMadufqFEbTayfbuoyM9SVBvD8472eqAR9hWifaMSaOkzkaRgwpjsf4u9Ni8ANoVmHzlo33BkNVBt&client_assertion_type=urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer&client_assertion=eyJraWQiOiJzaWdzYWc2MDgiLCJhbGciOiJSUzI1NiJ9.eyJpc3MiOiJmMTg5OTFhZi0zZWM5LTRmOTMtOTYzYi04ZWE0ZDA0ZWU4MDIiLCJhdWQiOiJodHRwczovL3Rlc3QuaWRwb3J0ZW4ubm8iLCJqdGkiOiIyMDBjNzY1OC1kNWY0LTQzMDEtYTIzZi02MWY0MjZjYzBjOGUiLCJpYXQiOjE2OTU3OTg2MDUsImV4cCI6MTY5NTc5ODY2NX0.OwShBU3K2SSw2vLn-XrH9R-B7gha4G-KyW9ctpJc74Q3coEFHB3zgJjOvme7yo2k9lXOGllSMnI452D4XPxq7qSdG991PkiCdS-D3cLqDOM9uIQkAPUjfO_BrEnrVS5vgUtTSevzGSULrIdx6bpgBPsuWjfShZG8qv9n9wDBa8aYIDiAyC5iuNhWhkhl-1fllCnyr9zh9yvVAkmoWB2yhaC0kEALCEuF1ORB9fnJ60-MmcoC_ONwgJ1G9FyI2LFI68FD61Oxqzwk5S05Mc0a9IleEjMUurW9BMtYAvK8pQRhWNlKqcTeTL5wzBVYH_B0DtfMRii26Hk68Iq75v-Z9g < 400 Bad Request set-cookie: dtCookie=v_4_srv_67_sn_72FF0894BEE405509D87E37015BBE790_perc_100000_ol_0_mul_1_app-3Aea7c4b59f27d43eb_0; Path=/; Domain=.idporten.no x-oneagent-js-injection: true server-timing: dtRpid;desc="-6698218", dtSInfo;desc="0" cache-control: no-store pragma: no-cache content-type: application/json;charset=UTF-8 content-length: 106 date: Wed, 27 Sep 2023 07:10:04 GMT set-cookie: ae8f6e07cbd4dde8431e58944ce42790=1b858d65f3138ecf9649b6a18cb0936b; path=/; HttpOnly; Secure; SameSite=None connection: close Set-Cookie: BIGipServer~DigDir~pool_digdir_test.idporten.no_https=rd3535o00000000000000000000ffff8b6920d1o443; path=/; Httponly; Secure Strict-Transport-Security: max-age=16070400; includeSubDomains {"error":"invalid_request","error_description":"Invalid request: Missing subject in client JWT assertion"} ```