external-auth-server: eas fails to handle x-userinfo with non-ascii characters

Hi Travis,

having a user in our OIDC IAM with non-ascii chars in the first- and lastname (not in the username)

leads to this:

eas-hfpsk external-auth-server 2022-10-26T20:45:18.185532248+02:00 
{"code":"ERR_INVALID_CHAR","level":"error","message":"Invalid character in header content [\"X-Userinfo\"]",
"service":"external-auth-server","stack":"TypeError [ERR_INVALID_CHAR]: Invalid character in header content 
[\"X-Userinfo\"]\n    at ServerResponse.setHeader (node:_http_outgoing:606:3)\n    at ServerResponse.header 
(/home/eas/app/node_modules/express/lib/response.js:794:10)\n    at Function.setResponse 
(/home/eas/app/src/index.js:19:11)\n    at /home/eas/app/src/server.js:533:28\n    at runMicrotasks (<anonymous>)\n    
at processTicksAndRejections (node:internal/process/task_queues:96:5)\n    at async verifyHandler 
(/home/eas/app/src/server.js:93:12)","timestamp":"2022-10-26T18:45:18.184Z"}

It’s reproducible with Keycloak as IAM as well.