500 Error on custom authentication callback (keycloak)

**Describe the bug**

Error HTTP 500 on Custom authentication (Keycloak) callback. No logs provided by Azure Static Webapp.

The /auth call passes and redirects to the callback but then I have a timeout and a 500 error.

`staticwebapp.config.json`
```
{
"routes": [
{
"route": "/*",
"allowedRoles": ["authenticated"]
}
],
"navigationFallback": {
"rewrite": "/index.html"
},
"responseOverrides": {
"401": {
"redirect": "/.auth/login/keycloak",
"statusCode": 302
}
},
"auth": {
"identityProviders": {
"customOpenIdConnectProviders": {
"keycloak": {
"registration": {
"clientIdSettingName": "CLIENT_ID",
"clientCredential": {
"clientSecretSettingName": "CLIENT_SECRET"
},
"openIdConnectConfiguration": {
"wellKnownOpenIdConfiguration": "https://keycloakinstance.com/auth/realms/myrealm/.well-known/openid-configuration"
}
},
"login": {
"nameClaimType": "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name",
"scopes": ["openid", "offline_access", "email"],
"loginParameterNames": []
}
}
}
}
}
}

```

@mkarmark or someone from azure, would you mind checking on your end what's happening ? It is so annoying to not have any logs of what is happening with authentication... I can DM you the static webapp URL, don't want to put it here publicly