Add Device ID validation

Currently the SDK does not validate the device ID and since it uses it to build the publish topic (instead of reading the certificate Common Name, like other SDKs) this could lead to devices being disconnected at the broker level (since they try to subscribe to topics for which they're not authorized).

The SDK should perform validation on the provided Device ID, and should possibly also use the Common Name of the certificate received from Pairing API as base for the device topic.

No files or tests are named. Start by tracing how the provided Device ID is used to build publish topics and how the Pairing API certificate Common Name is exposed; determine the validation rules and whether the certificate identity should be authoritative. Done means invalid or mismatched identities cannot produce broker-unauthorized topics, with coverage for the resulting behavior.

Written by the indexing model from the issue text.