Do not add Accept-Ranges header on client-side

This commit fixes a regression that added the Accept-Ranges header on
both client and server. Accept-Ranges is response header, so we now make
sure it only appears on the server side.

See gh-28291

spring-web/src/main/java/org/springframework/http/codec/ResourceHttpMessageWriter.java

@@ -145,7 +145,10 @@ public void addHeaders(ReactiveHttpOutputMessage message, Resource resource, @Nu
 				headers.setContentLength(length);
 			}
 		}
-		headers.set(HttpHeaders.ACCEPT_RANGES, "bytes");
+		if (message instanceof ServerHttpResponse) {
+			// server side
+			headers.set(HttpHeaders.ACCEPT_RANGES, "bytes");
+		}
 	}
 
 	private static MediaType getResourceMediaType(

spring-web/src/test/java/org/springframework/http/codec/ResourceHttpMessageWriterTests.java

@@ -25,13 +25,16 @@
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import org.springframework.core.ResolvableType;
 import org.springframework.core.io.ByteArrayResource;
 import org.springframework.core.io.Resource;
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRange;
 import org.springframework.http.HttpStatus;
 import org.springframework.util.MimeTypeUtils;
 import org.springframework.util.StringUtils;
+import org.springframework.web.testfixture.http.client.reactive.MockClientHttpRequest;
 import org.springframework.web.testfixture.http.server.reactive.MockServerHttpRequest;
 import org.springframework.web.testfixture.http.server.reactive.MockServerHttpResponse;
 
@@ -66,7 +69,7 @@ public void getWritableMediaTypes() throws Exception {
 	}
 
 	@Test
-	public void writeResource() throws Exception {
+	public void writeResourceServer() throws Exception {
 
 		testWrite(get("/").build());
 
@@ -78,6 +81,21 @@ public void writeResource() throws Exception {
 		StepVerifier.create(this.response.getBodyAsString()).expectNext(content).expectComplete().verify();
 	}
 
+	@Test
+	public void writeResourceClient() throws Exception {
+
+		MockClientHttpRequest request = new MockClientHttpRequest(HttpMethod.GET, "/");
+		Mono<Void> mono = this.writer.write(this.input, ResolvableType.forClass(Resource.class), TEXT_PLAIN, request, HINTS);
+		StepVerifier.create(mono).expectComplete().verify();
+
+		assertThat(request.getHeaders().getContentType()).isEqualTo(TEXT_PLAIN);
+		assertThat(request.getHeaders().getContentLength()).isEqualTo(39L);
+		assertThat(request.getHeaders().getFirst(HttpHeaders.ACCEPT_RANGES)).isNull();
+
+		String content = "Spring Framework test resource content.";
+		StepVerifier.create(request.getBodyAsString()).expectNext(content).expectComplete().verify();
+	}
+
 	@Test
 	public void writeSingleRegion() throws Exception {