Incorporate quickstart changes in security-openid-connect-client guide

[albers]

quarkusio/quarkus-quickstarts#1140 renamed two classes and two fields so that the demo more clearly communicates the usage of the RequestFilters.

This PR aligns the corresponding guide to these changes.

It also fixes some occurrances of wrong endpoints that #26372 missed.

A third commit brings unrelated small improvements (boy scout rule).

The reason for my change in the curl options (-i instead -v) is: -v produces a lot of output and is more tailored to debugging purposes. In this example, we want so see the response codes, which can be seen more easily when using the -i option, which adds the headers to the output.

with -v

$ curl -v http://localhost:8080/frontend/user-name-with-oidc-client-token
* STATE: INIT => CONNECT handle 0x80008f0f8; line 1835 (connection #-5000)
* Added connection 0. The cache now contains 1 members
* family0 == v4, family1 == v6
*   Trying 127.0.0.1:8080...
* STATE: CONNECT => CONNECTING handle 0x80008f0f8; line 1896 (connection #0)
* Connected to localhost (127.0.0.1) port 8080 (#0)
* STATE: CONNECTING => PROTOCONNECT handle 0x80008f0f8; line 2028 (connection #0)
* STATE: PROTOCONNECT => DO handle 0x80008f0f8; line 2051 (connection #0)
> GET /frontend/user-name-with-oidc-client-token HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.81.0
> Accept: */*
>
* STATE: DO => DID handle 0x80008f0f8; line 2147 (connection #0)
* STATE: DID => PERFORMING handle 0x80008f0f8; line 2266 (connection #0)
* Mark bundle as not supporting multiuse
* HTTP 1.1 or later with persistent connection
< HTTP/1.1 200 OK
< content-length: 5
< Content-Type: text/plain;charset=UTF-8
<
* STATE: PERFORMING => DONE handle 0x80008f0f8; line 2465 (connection #0)
* multi_done: status: 0 prem: 0 done: 0
* Connection #0 to host localhost left intact
* Expire cleared (transfer 0x80008f0f8)
alice

with -i

$ curl -i http://localhost:8080/frontend/user-name-with-oidc-client-token
HTTP/1.1 200 OK
content-length: 5
Content-Type: text/plain;charset=UTF-8

alice

I'm fine with a squashed merge. I separated the changes by concern for easier reviewability.

Please let me know if I should drop certain changes from this PR.

[sberyozkin]

Thanks