Keycloak DevService: Improve error messages and documentation #34756

Job	Run time
CI Sanity Check	32s
Attach pull request number	3s
Initial JDK 11 Build	22m 27s
Calculate Test Jobs	9s
JVM Tests - JDK 11	18m 38s
Maven Tests - JDK 11	8m 50s
JVM Tests - JDK 17	26m 5s
Devtools Tests - JDK ${{ matrix.java.name }}	0s
Gradle Tests - JDK ${{ matrix.java.name }}	0s
JVM Tests - JDK 21	18m 35s
Maven Tests - JDK 11 Windows	12m 30s
JVM Tests - JDK 17 Windows	7m 6s
Kubernetes Tests - JDK ${{ matrix.java.name }}	0s
Quickstarts Compilation - JDK 17	7m 22s
MicroProfile TCKs Tests	0s
Native Tests - Security2	38m 16s
Native Tests - Virtual Thread - ${{ matrix.category }}	0s
Native Tests - Security3	5m 44s
Build report	12s
	2h 46m 29s

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