[improve][client] Add newMessage with schema and transactions

[omarkj]

Pulsar Client allows callers to create messages with a schema or a transaction, but not both.

This commit adds a new method in the producer that allows callers to create a message with both a schema and transaction.

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[dao-jun]

For PIP process, pls referring to https://github.com/apache/pulsar/tree/master/pip#pulsar-improvement-proposal-pip

[omarkj]

PIP PR filed here: #23950, will follow those guidelines by emailing out to the thread soon, etc.

[lhotari]

LGTM

[lhotari]

@BewareMyPower @dao-jun The PIP has been approved and merged, https://github.com/apache/pulsar/blob/master/pip/pip-407.md . PTAL and review

[lhotari]

I have a concern about backward compatibility with this interface change. Adding a new method without a default implementation will break source compatibility for any custom implementations of the Producer interface.
While it might be uncommon for users to implement this interface directly, it could happen in testing scenarios or custom proxy implementations. Java source compatibility rules require all implementors to provide all interface methods.

We could address the source compatibility issue by adding a default implementation:

Suggested change

	<V> TypedMessageBuilder<V> newMessage(Schema<V> schema,
	Transaction txn);
	default <V> TypedMessageBuilder<V> newMessage(Schema<V> schema, Transaction txn) {
	// to retain source compatibilty of Producer interface for implementors of the Producer interface
	throw new UnsupportedOperationException(
	String.format("Method not implemented in: %s", getClass().getName()));
	}

The benefit of making it source compatible is that we could also backport this change to the 4.0.x client without introducing breaking changes.