[FEATURE] Allow connectors to override CloudEvent attributes via user properties (don't block or ignore them)

[felixse]

Product

Rust SDK

Azure Iot Operations version

azure_iot_operations_mqtt = "1.0.2"
azure_iot_operations_protocol = "1.0.0"
azure_iot_operations_services = "1.2.0"
azure_iot_operations_connector = "2.0.1"

What happened?

When a connector forwards data through the managed ADR DataOperationClient /
Forwarder, the SDK generates the CloudEvent attributes (id, source, type,
subject, specversion, time, datacontenttype, dataschema) itself. A
connector currently has no way to override any of these: if it supplies a
user property with a reserved CloudEvent name, the message is rejected at build
time rather than the connector's value being used.

Request: a connector should be able to set/override any CloudEvent attribute by
passing it as a user property, and the SDK should honor that value instead of
blocking it or silently discarding it.

List the steps to reproduce

No response

Code of Conduct

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[avishekpant]

Felix Seidl (@felixse) - QQ: Which user properties would you like to be able to override?

[felixse]

Avishek (@avishekpant) basically any cloud event header that is defined here:

iot-operations-sdks/rust/azure_iot_operations_connector/src/destination_endpoint.rs

Line 355 in 896615d

fn build_cloud_event_headers(