Restore compatibility in whitespace detection (#4692)

`String.trim()` is now used consistently.

See #3824 (comment)
for details.

Author: vdmitrienko

junit-jupiter-params/src/main/java/org/junit/jupiter/params/provider/CsvFileSource.java

@@ -225,6 +225,9 @@
 	 * Controls whether leading and trailing whitespace characters of unquoted
 	 * CSV columns should be ignored.
 	 *
+	 * <p>Whitespace refers to characters with Unicode code points less than
+	 * or equal to {@code U+0020}, as defined by {@link String#trim()}.
+	 *
 	 * <p>Defaults to {@code true}.
 	 *
 	 * @since 5.8

junit-jupiter-params/src/main/java/org/junit/jupiter/params/provider/CsvReaderFactory.java

@@ -165,7 +165,7 @@ public String modify(long unusedStartingLineNumber, int unusedFieldIdx, boolean
 			if (!quoted && field.isBlank()) {
 				return NULL_MARKER;
 			}
-			String modifiedField = (!quoted && ignoreLeadingAndTrailingWhitespaces) ? field.strip() : field;
+			String modifiedField = (!quoted && ignoreLeadingAndTrailingWhitespaces) ? field.trim() : field;
 			if (nullValues.contains(modifiedField)) {
 				return NULL_MARKER;
 			}

junit-jupiter-params/src/main/java/org/junit/jupiter/params/provider/CsvSource.java

@@ -286,6 +286,9 @@
 	 * Controls whether leading and trailing whitespace characters of unquoted
 	 * CSV columns should be ignored.
 	 *
+	 * <p>Whitespace refers to characters with Unicode code points less than
+	 * or equal to {@code U+0020}, as defined by {@link String#trim()}.
+	 *
 	 * <p>Defaults to {@code true}.
 	 *
 	 * @since 5.8

jupiter-tests/src/test/java/org/junit/jupiter/params/provider/CsvArgumentsProviderTests.java

@@ -126,6 +126,17 @@ void trimsTrailingSpaces() {
 		assertThat(arguments).containsExactly(new Object[][] { { "1", "" }, { "2", "" }, { "3", "" }, { "4", "" } });
 	}
 
+	@Test
+	void trimsSpacesUsingStringTrim() {
+		// \u0000 (null) removed by trim(), preserved by strip()
+		// \u00A0 (non-breaking space) preserved by trim(), removed by strip()
+		var annotation = csvSource().lines("\u0000foo,\u00A0bar", "\u0000' foo',\u00A0' bar'").build();
+
+		var arguments = provideArguments(annotation);
+
+		assertThat(arguments).containsExactly(array("foo", "\u00A0bar"), array(" foo", "\u00A0' bar'"));
+	}
+
 	@Test
 	void ignoresLeadingAndTrailingSpaces() {
 		var annotation = csvSource().lines("1,a", "2, b", "3,c ", "4, d ") //