Make ImageData class public for custom image pull policies (#2585)

* Making imagedata public so it can be used to create custom image pull
policies. Adding test to ensure it works as expected.

* Ensuring we don't do unnecessary pulls and using the default generic
container image for the out of package pull policy test.

Co-authored-by: Chason Choate <chason.choate@digitalreasoning.com>
Co-authored-by: Richard North <rich.north@gmail.com>

core/src/main/java/org/testcontainers/images/ImageData.java

@@ -10,7 +10,7 @@
 
 @Value
 @Builder
-class ImageData {
+public class ImageData {
 
     @NonNull
     Instant createdAt;

core/src/test/java/alt/testcontainers/README.md

@@ -0,0 +1 @@
+Useful place for running tests that need to be outside of the `org.testcontainers` package.

core/src/test/java/alt/testcontainers/images/OutOfPackageImagePullPolicyTest.java

@@ -0,0 +1,27 @@
+package alt.testcontainers.images;
+
+import org.junit.Test;
+import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.containers.startupcheck.OneShotStartupCheckStrategy;
+import org.testcontainers.images.AbstractImagePullPolicy;
+import org.testcontainers.images.ImageData;
+import org.testcontainers.utility.DockerImageName;
+
+public class OutOfPackageImagePullPolicyTest {
+    @Test
+    public void shouldSupportCustomPoliciesOutOfTestContainersPackage() {
+        try (
+            GenericContainer<?> container = new GenericContainer<>()
+                .withImagePullPolicy(new AbstractImagePullPolicy() {
+                    @Override
+                    protected boolean shouldPullCached(DockerImageName imageName, ImageData localImageData) {
+                        return false;
+                    }
+                })
+        ) {
+            container.withStartupCheckStrategy(new OneShotStartupCheckStrategy());
+            container.start();
+        }
+    }
+
+}