KeyCloak URLs should not be constructed with the auth-server-url but with the openid-configuration response

### Describe the bug

Currently the realmUrl and other URLs are constructed by prefixing them with the auth-server-url from the config file. The auth-server-url should only be uses to get the openid-configuration:

/realms//.well-known/openid-configuration

In the response of this request you can get all necessary urls (eg logout, autohorization-endpoint,...)

### Version

12

### Expected behavior

Get all openid related endpoints from /realms//.well-known/openid-configuration

### Actual behavior

https://github.com/keycloak/keycloak-nodejs-connect/blob/dd1c20f0c1e6366e98434128eafea2e78ab545fd/middleware/auth-utils/config.js#L125
https://github.com/keycloak/keycloak-nodejs-connect/blob/dd1c20f0c1e6366e98434128eafea2e78ab545fd/middleware/auth-utils/config.js#L131
https://github.com/keycloak/keycloak-nodejs-connect/blob/dd1c20f0c1e6366e98434128eafea2e78ab545fd/keycloak.js#L388
https://github.com/keycloak/keycloak-nodejs-connect/blob/dd1c20f0c1e6366e98434128eafea2e78ab545fd/keycloak.js#L403

### How to Reproduce?

_No response_

### Anything else?

_No response_

Start by reading middleware/auth-utils/config.js around lines 125 and 131, then keycloak.js around lines 388 and 403. Trace how the auth-server-url is used and how the realm's .well-known/openid-configuration response could supply the OpenID endpoints. Done means the related endpoints are obtained from that response rather than constructed from the configured server URL.

Written by the indexing model from the issue text.