Copy cookies in built ServerResponse

Closes gh-22481

Author: poutsma

spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultServerResponseBuilder.java

@@ -70,6 +70,7 @@ public DefaultServerResponseBuilder(ServerResponse other) {
 		this.statusCode = (other instanceof AbstractServerResponse ?
 				((AbstractServerResponse) other).statusCode : other.statusCode().value());
 		this.headers.addAll(other.headers());
+		this.cookies.addAll(other.cookies());
 	}
 
 	public DefaultServerResponseBuilder(HttpStatus status) {

spring-webmvc/src/test/java/org/springframework/web/servlet/function/DefaultServerResponseBuilderTests.java

@@ -71,10 +71,15 @@ public void status() {
 
 	@Test
 	public void from() {
-		ServerResponse other = ServerResponse.ok().header("foo", "bar").build();
+		Cookie cookie = new Cookie("foo", "bar");
+		ServerResponse other = ServerResponse.ok()
+				.header("foo", "bar")
+				.cookie(cookie)
+				.build();
 		ServerResponse result = ServerResponse.from(other).build();
 		assertEquals(HttpStatus.OK, result.statusCode());
 		assertEquals("bar", result.headers().getFirst("foo"));
+		assertEquals(cookie, result.cookies().getFirst("foo"));
 	}