Fix hasMessageAvailable incorrectly returns true when read to latest after seeking by timestamp

[BewareMyPower]

The computation for compareMarkDeletePosition is wrong that hasSoughtByTimestamp_ should only be checked when lastDequedMessageId_ is earliest, which means no messages have been received.

Additionally, reset startMessageId_ when seeking by timestamp, otherwise, if the initial startMessageId of a reader is a valid message id, that message could be filtered in

pulsar-client-cpp/lib/ConsumerImpl.cc

Lines 619 to 625 in 9b86f9e

	if (isPersistent_ && startMessageId &&
	m.getMessageId().ledgerId() == startMessageId.value().ledgerId() &&
	m.getMessageId().entryId() == startMessageId.value().entryId() &&
	isPriorEntryIndex(m.getMessageId().entryId())) {
	LOG_DEBUG(getName() << " Ignoring message from before the startMessageId: "
	<< startMessageId.value());
	return;

or

pulsar-client-cpp/lib/ConsumerImpl.cc

Lines 774 to 780 in 9b86f9e

	if (isPersistent_ && msgId.ledgerId() == startMessageId.value().ledgerId() &&
	msgId.entryId() == startMessageId.value().entryId() &&
	isPriorBatchIndex(msgId.batchIndex())) {
	LOG_DEBUG(getName() << "Ignoring message from before the startMessageId"
	<< msg.getMessageId());
	++skippedMessages;
	continue;

Improve testHasMessageAvailableAfterSeekTimestamp to cover the cases above.

[Copilot]

Pull Request Overview

This PR fixes a bug where hasMessageAvailable incorrectly returns true when reading to the latest message after seeking by timestamp. The fix involves correcting the logic for determining when to compare mark delete positions and properly resetting the start message ID when seeking by timestamp.

Key changes:

• Modified compareMarkDeletePosition logic to only use hasSoughtByTimestamp_ check when no messages have been received
• Reset startMessageId_ to prevent message filtering issues after timestamp seeks
• Enhanced test coverage to validate the fix by reading all available messages after seeking

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
lib/ConsumerImpl.h	Added helper method hasSoughtByTimestamp() for consistent atomic access
lib/ConsumerImpl.cc	Fixed compareMarkDeletePosition logic and startMessageId_ handling for timestamp seeks
tests/ReaderTest.cc	Enhanced test to validate fix by consuming all messages after seeking by timestamp

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