Add HttpHeaders#setAcceptLanguageAsLocale(Locale)

Issue: SPR-15024

Author: sdeleuze

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

@@ -475,6 +475,15 @@ public List<Locale.LanguageRange> getAcceptLanguage() {
 		return Collections.emptyList();
 	}
 
+	/**
+	 * A variant of {@link #setAcceptLanguage(List)} that sets the {@literal Accept-Language}
+	 * header value to the specified locale.
+	 * @since 5.0
+	 */
+	public void setAcceptLanguageAsLocale(Locale locale) {
+		setAcceptLanguage(Collections.singletonList(new Locale.LanguageRange(locale.toLanguageTag())));
+	}
+
 	/**
 	 * A variant of {@link #getAcceptLanguage()} that converts each
 	 * {@link java.util.Locale.LanguageRange} to a {@link Locale} and returns

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

@@ -438,6 +438,9 @@ public void acceptLanguage() {
 		assertEquals(expectedRanges, headers.getAcceptLanguage());
 
 		assertEquals(Locale.forLanguageTag("fr-ch"), headers.getAcceptLanguageAsLocale());
+
+		headers.setAcceptLanguageAsLocale(Locale.FRANCE);
+		assertEquals(Locale.FRANCE, headers.getAcceptLanguageAsLocale());
 	}
 
 	@Test