POST /realms/test/protocol/openid-connect/token
Authorization: Basic cmVxdWVzdGVyLWNsaWVudDpwYXNzd29yZA==
Content-Type: application/x-www-form-urlencoded
Accept: application/json
grant_type=urn:ietf:params:oauth:grant-type:token-exchange&
subject_token=$SUBJECT_TOKEN&
subject_token_type=urn:ietf:params:oauth:token-type:access_token&
requested_token_type=urn:ietf:params:oauth:token-type:access_token