Refine logback support

This commit restores and refines the LogBack substitution to relax
the check on XML files since there is already a check at build
time in LogbackHints and @aclement found a related issue.

The documentation has been updated to recommend using embedded
logback-spring.xml and the logger sample is now mentioned.

Closes gh-1505

samples/logger/build.sh

@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 
-${PWD%/*samples/*}/scripts/compileWithMaven.sh $* &&  ${PWD%/*samples/*}/scripts/test.sh $* --logging.config=src/main/resources/logback-config.xml
+${PWD%/*samples/*}/scripts/compileWithMaven.sh $* &&  ${PWD%/*samples/*}/scripts/test.sh $*

spring-native-docs/src/main/asciidoc/support.adoc

@@ -148,8 +148,8 @@ implementation("org.springframework.boot:spring-boot-starter-actuator") {
 * `spring-boot-starter-jdbc`
 * `spring-boot-starter-logging`
 ** Logback is supported with some limitations
-*** Configuration with `logback.xml` embedded in the application https://github.com/spring-projects-experimental/spring-native/issues/625[is not supported yet].
-*** Logback XML configuration via `myapp -Dlogging.config=logback-config.xml` or `myapp --logging.config==logback-config.xml` is supported but you need to enable <<spring-aot-configuration, XML support>> and add https://search.maven.org/artifact/org.codehaus.janino/janino[`org.codehaus.janino:janino` dependency].
+*** Configuration with embedded `logback.xml` https://github.com/spring-projects-experimental/spring-native/issues/625[is not supported yet].
+*** Configuration with embedded `logback-spring.xml`, via `myapp -Dlogging.config=logback-config.xml` or `myapp --logging.config=logback-config.xml` is supported but you need to enable <<aot-build-setup-configuration, XML support>> and add https://search.maven.org/artifact/org.codehaus.janino/janino[`org.codehaus.janino:janino` dependency] (see the `logger` sample).
 *** http://logback.qos.ch/manual/configuration.html#conditional[Conditional processing in Logback] configuration with Janino library has limited support. Only simple expressions of `isDefined()` and `isNull()` having string literal as argument are supported.
 *** See <<logback-workaround, this workaround>> to configure it programmatically.
 ** Log4j2 is not supported yet, see https://github.com/spring-projects-experimental/spring-native/issues/115[#115].

spring-native/src/main/java/org/springframework/nativex/substitutions/logback/Target_ContextInitializer.java

@@ -42,8 +42,6 @@ public void configureByResource(URL url) throws JoranException {
 		final String urlString = url.toString();
 		if (urlString.endsWith("groovy")) {
 			throw new LogbackException("Logback Groovy configuration is not supported on native");
-		} else if (urlString.endsWith("xml")) {
-			throw new LogbackException("Logback XML configuration is not supported yet, see https://github.com/spring-projects-experimental/spring-native/issues/625");
 		}
 	}
 }