Add requestFactorySettings method to RestTemplateBuilder

Add a `requestFactorySettings` method to `RestTemplateBuilder` to make
it easier to apply an existing `ClientHttpRequestFactorySettings`
instance.

Closes gh-42885

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/client/RestTemplateBuilder.java

@@ -429,6 +429,22 @@ public class RestTemplateBuilder {
 				this.customizers, this.requestCustomizers);
 	}
 
+	/**
+	 * Sets the {@link ClientHttpRequestFactorySettings}. This will replace any previously
+	 * set {@link #connectTimeout(Duration) connectTimeout} ,{@link #readTimeout(Duration)
+	 * readTimeout} and {@link #sslBundle(SslBundle) sslBundle} values.
+	 * @param requestFactorySettings the request factory settings
+	 * @return a new builder instance
+	 * @since 3.4.0
+	 */
+	public RestTemplateBuilder requestFactorySettings(ClientHttpRequestFactorySettings requestFactorySettings) {
+		Assert.notNull(requestFactorySettings, "ClientHttpRequestFactorySettings must not be null");
+		return new RestTemplateBuilder(requestFactorySettings, this.detectRequestFactory, this.rootUri,
+				this.messageConverters, this.interceptors, this.requestFactoryBuilder, this.uriTemplateHandler,
+				this.errorHandler, this.basicAuthentication, this.defaultHeaders, this.customizers,
+				this.requestCustomizers);
+	}
+
 	/**
 	 * Sets the connection timeout on the underlying {@link ClientHttpRequestFactory}.
 	 * @param connectTimeout the connection timeout

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/client/RestTemplateBuilderTests.java

@@ -18,6 +18,7 @@ package org.springframework.boot.web.client;
 
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Set;
@@ -30,6 +31,7 @@ import org.mockito.InOrder;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 
+import org.springframework.boot.http.client.ClientHttpRequestFactorySettings;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
@@ -272,9 +274,8 @@ class RestTemplateBuilderTests {
 
 	@Test
 	void requestFactoryWhenFunctionIsNullShouldThrowException() {
-		assertThatIllegalArgumentException()
-			.isThrownBy(() -> this.builder
-				.requestFactory((Function<ClientHttpRequestFactorySettings, ClientHttpRequestFactory>) null))
+		assertThatIllegalArgumentException().isThrownBy(() -> this.builder.requestFactory(
+				(Function<org.springframework.boot.web.client.ClientHttpRequestFactorySettings, ClientHttpRequestFactory>) null))
 			.withMessageContaining("RequestFactoryFunction must not be null");
 	}
 
@@ -343,6 +344,14 @@ class RestTemplateBuilderTests {
 		assertThat(request.getHeaders()).contains(entry("spring", Collections.singletonList("boot")));
 	}
 
+	@Test
+	void requestFactorySettingsAppliesSettings() {
+		ClientHttpRequestFactorySettings settings = ClientHttpRequestFactorySettings.defaults()
+			.withConnectTimeout(Duration.ofSeconds(1));
+		RestTemplate template = this.builder.requestFactorySettings(settings).build();
+		assertThat(template.getRequestFactory()).extracting("connectTimeout").isEqualTo(1000L);
+	}
+
 	@Test
 	void requestCustomizersAddsCustomizers() {
 		RestTemplate template = this.builder