Fix error mark position for PatternParseException

PatternParseException.toDetailedString() return a String
with a mark to specify the error position in the pattern.
The mark takes place in the second line in the String
returned. Because PatternParseFailureAnalyzer.analyze
appended "Invalid mapping pattern detected:" at the
beginning of the returned String, the mark was not well
positioned.

Now, a "\n" is inserted after "Invalid mapping pattern detected:"
and the mark is well positioned

See gh-38944

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/diagnostics/analyzer/PatternParseFailureAnalyzer.java

@@ -30,7 +30,7 @@ class PatternParseFailureAnalyzer extends AbstractFailureAnalyzer<PatternParseEx
 
 	@Override
 	protected FailureAnalysis analyze(Throwable rootFailure, PatternParseException cause) {
-		return new FailureAnalysis("Invalid mapping pattern detected: " + cause.toDetailedString(),
+		return new FailureAnalysis("Invalid mapping pattern detected:\n" + cause.toDetailedString(),
 				"Fix this pattern in your application or switch to the legacy parser implementation with "
 						+ "'spring.mvc.pathmatch.matching-strategy=ant_path_matcher'.",
 				cause);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/diagnostics/analyzer/PatternParseFailureAnalyzerTests.java

@@ -36,10 +36,14 @@ class PatternParseFailureAnalyzerTests {
 	@Test
 	void patternParseFailureQuotesPattern() {
 		FailureAnalysis failureAnalysis = performAnalysis("/spring/**/framework");
-		assertThat(failureAnalysis.getDescription()).contains("Invalid mapping pattern detected: /spring/**/framework");
+		assertThat(failureAnalysis.getDescription()).contains("""
+				Invalid mapping pattern detected:
+				/spring/**/framework
+				       ^
+				""");
 		assertThat(failureAnalysis.getAction())
-			.contains("Fix this pattern in your application or switch to the legacy parser"
-					+ " implementation with 'spring.mvc.pathmatch.matching-strategy=ant_path_matcher'.");
+				.contains("Fix this pattern in your application or switch to the legacy parser"
+						+ " implementation with 'spring.mvc.pathmatch.matching-strategy=ant_path_matcher'.");
 	}
 
 	private FailureAnalysis performAnalysis(String pattern) {