[Service Bus] Apply link metadata for the maximum batch message count

[jsquire]

Problem statement

There is a maximum number of items that the service will accept in a single operation, regardless of any size considerations. At the time of writing, the Service Bus service will reject any request containing more than 4,500 messages. Because the service doesn't communicate the object limit, the client library is unable to validate that constraint or provide a guided development experience for ensuring safe limits.

There is an open request for the service to add a new link property that exposes the maximum batch message count on an AMQP link so that callers can dynamically discover the service limits.

Current work-around

The CreateMessageBatchOptions type is currently hardcoding the 4,500 message limit in order to ensure that the client library does not allow callers to create batches which cannot be successfully published.

Scope of work

• Update AmqpSender to consume the maximum batch message count when a link is opened, following the same pattern used for the maximum message size, setting the MaxMessageCount property.

Success criteria

• The MaxMessageCount property of AmqpSender is populated dynamically from AMQP link metadata and is updated each time a link is opened.
• The Service Bus live test suite continues to pass reliably.

References and related

• Request for additional sending link metadata for service limitations (#708)

[jsquire]

depends on #709