ValkeyCacheService: pluggable ObjectInputStream for cross-relocation reads

[frew]

Why

MailFoo shares one Valkey Objectify entity cache across processes that relocate com.google.* (Guava, protobuf) differently in their shadowJars (app server = un-relocated; ServerSpark/JettyServers = streak.-relocated). ValkeyCacheService.deserialize used a plain ObjectInputStream, and JDK serialization embeds the writer's class names, so a relocated writer's entry fails in an un-relocated reader with:

ClassNotFoundException: streak.com.google.common.collect.ImmutableList$SerializedForm

Change

• Add an ObjectInputStreamFactory hook; deserialize builds its stream through it. Defaults to a plain ObjectInputStream, so existing callers are unaffected.
• MailFoo supplies a KeySubstitutingObjectInputStream that bridges shaded ↔ canonical names (in readClassDescriptor(), the only hook allowed to substitute a differently-named class post-JDK-17).
• New constructors: (client, factory) and (client, ttl, factory).

Tests

• Added injectedFactoryRemapsClassNamesOnRead (descriptor swap honored on the read path) and factoryConstructorRoundTripsAndAppliesDefaultTtl.
• Retains all prior behavior (compression, TTL, CAS) — this is -7 plus the factory hook, published as 6.1.4-streak-valkey-8.

Note: the Valkey testcontainers suite requires Docker; test-compile and the new logic were verified locally.

[gemini-code-assist]

Code Review

This pull request introduces an ObjectInputStreamFactory functional interface to ValkeyCacheService, allowing callers to supply custom ObjectInputStream implementations (e.g., for class name remapping during deserialization). It adds new constructors to accept this factory, updates the deserialization logic to use it, and includes corresponding unit tests. The feedback suggests adding defensive null checks for the client parameter in the constructor and for the ObjectInputStream returned by the factory to prevent potential NullPointerExceptions.

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[gemini-code-assist]

The client parameter is a required dependency for ValkeyCacheService but is currently assigned directly without a null check. To prevent potential NullPointerExceptions later during cache operations, it is recommended to enforce defensive programming by validating that client is not null using Objects.requireNonNull.

Suggested change

	this.client = client;
	this.client = Objects.requireNonNull(client, "client");

[gemini-code-assist]

If a custom ObjectInputStreamFactory implementation incorrectly returns null, calling ois.readObject() will throw a generic NullPointerException. To adhere to defensive programming practices, we should check if the returned ObjectInputStream is null using Objects.requireNonNull.

Suggested change

	final ObjectInputStream ois = objectInputStreamFactory.create(bais)) {
	return ois.readObject();
	final ObjectInputStream ois = Objects.requireNonNull(objectInputStreamFactory.create(bais), "ObjectInputStreamFactory returned null")) {
	return ois.readObject();