Match ContentDisposition attributes case-insensitively

This commit ensures that `ContentDisposition` parses attributes like
"filename" and "filename*" in a case insensitive fashion, per RFC 6266.

Closes gh-34383

Signed-off-by: Andras Dobrosi <dobrosi@gmail.com>
[brian.clozel@broadcom.com: apply code conventions]
Signed-off-by: Brian Clozel <brian.clozel@broadcom.com>

Author: dobrosi

spring-web/src/main/java/org/springframework/http/ContentDisposition.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,7 @@
 import java.util.Base64;
 import java.util.BitSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -354,7 +355,7 @@ public static ContentDisposition parse(String contentDisposition) {
 			String part = parts.get(i);
 			int eqIndex = part.indexOf('=');
 			if (eqIndex != -1) {
-				String attribute = part.substring(0, eqIndex);
+				String attribute = part.substring(0, eqIndex).toLowerCase(Locale.ROOT);
 				String value = (part.startsWith("\"", eqIndex + 1) && part.endsWith("\"") ?
 						part.substring(eqIndex + 2, part.length() - 1) :
 						part.substring(eqIndex + 1));

spring-web/src/test/java/org/springframework/http/ContentDispositionTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -223,6 +223,14 @@ void parseIgnoresInvalidDates() {
 						.build());
 	}
 
+	@Test
+	void parseAttributesCaseInsensitively() {
+		ContentDisposition cd = ContentDisposition.parse("form-data; Name=\"foo\"; FileName=\"bar.txt\"");
+		assertThat(cd.getName()).isEqualTo("foo");
+		assertThat(cd.getFilename()).isEqualTo("bar.txt");
+		assertThat(cd.toString()).isEqualTo("form-data; name=\"foo\"; filename=\"bar.txt\"");
+	}
+
 	@Test
 	void parseEmpty() {
 		assertThatIllegalArgumentException().isThrownBy(() -> parse(""));