Describe the bug
After updating azure-sdk-bom to 1.2.38 offset is not stored anymore in Azure Blob Storage.
This is not only breaking our monitoring but also partition switch is currently broken.

To Reproduce
Steps to reproduce the behavior:
Use azure-sdk-bom 1.2.38.
Observe offset is not stored anymore.

Code Snippet
This is caused by offsetString is not used in every place:

com.azure.messaging.eventhubs.models.EventContext#updateCheckpointAsync:
    public Mono<Void> updateCheckpointAsync() {
        if (eventData == null) {
            return Mono.empty();
        }
        Checkpoint checkpoint
            = new Checkpoint().setFullyQualifiedNamespace(partitionContext.getFullyQualifiedNamespace())
                .setEventHubName(partitionContext.getEventHubName())
                .setConsumerGroup(partitionContext.getConsumerGroup())
                .setPartitionId(partitionContext.getPartitionId())
                .setSequenceNumber(eventData.getSequenceNumber())
                .setOffset(eventData.getOffset());
        return this.checkpointStore.updateCheckpoint(checkpoint);
    }

But there should be a fallback in com.azure.messaging.eventhubs.checkpointstore.blob.BlobCheckpointStore#updateCheckpoint to use getOffset() when getOffsetString() returns null or empty until getOffset() is removed.

Expected behavior
offset is saved in Checkpoint store.

Screenshots

Setup (please complete the following information):

• Library/Libraries:

• azure-sdk-bom:1.2.38
• com.azure:azure-messaging-eventhubs-checkpointstore-blob:jar:1.21.0
• com.azure:azure-messaging-eventhubs:jar:5.21.0

• Java version: 21

Severity
This is a high critical defect, because it breaks partition switch and our grafana monitoring - we can't monitor consumer group lag.