Allow image Created date to be configurable

A `createdDate` option on the Maven `spring-boot:build-image` goal
and the Gradle `bootBuildImage` task can be used to set the `Created`
metadata field on a generated OCI image to a specified date or to
the current date.

Closes gh-28798

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootBuildImage.java

@@ -260,6 +260,16 @@ public abstract class BootBuildImage extends DefaultTask {
 		action.execute(this.launchCache);
 	}
 
+	/**
+	 * Returns the date that will be used as the {@code Created} date of the image. When
+	 * {@code null}, a fixed date that enables build reproducibility will be used.
+	 * @return the created date
+	 */
+	@Input
+	@Optional
+	@Option(option = "createdDate", description = "The date to use as the created date of the image")
+	public abstract Property<String> getCreatedDate();
+
 	/**
 	 * Returns the Docker configuration the builder will use.
 	 * @return docker configuration.
@@ -305,6 +315,7 @@ public abstract class BootBuildImage extends DefaultTask {
 		request = customizeTags(request);
 		request = customizeCaches(request);
 		request = request.withNetwork(getNetwork().getOrNull());
+		request = customizeCreatedDate(request);
 		return request;
 	}
 
@@ -387,4 +398,12 @@ public abstract class BootBuildImage extends DefaultTask {
 		return request;
 	}
 
+	private BuildRequest customizeCreatedDate(BuildRequest request) {
+		String createdDate = getCreatedDate().getOrNull();
+		if (createdDate != null) {
+			return request.withCreatedDate(createdDate);
+		}
+		return request;
+	}
+
 }