Asks a Core to connect to a camera with the address and credentials you supply, and returns whether the stream opened together with a snapshot from it. The camera does not have to be provisioned in Lumana — this is the check to run before adding one, or when a provisioned camera stopped working and you want to test a corrected password without saving it. Nothing is stored: the credentials in this request are forwarded to the Core for the single test and are not written to the camera record. To test every camera a Core already carries, use POST /v1/troubleshooting/cores/cameras-connection-test. The command is published to the Core and the HTTP response is held open until the device answers. On success the body is the device's own output merged with sessionId and state. state is a NUMBER, not a word - 0 completed, 1 the device did not answer in time, 2 the device reported an error, 3 the command was not sent because the Core was out of sync. A call that times out answers 408 with { message, state: 1, responseBody } and carries NO sessionId and no device output. The shape of the device output depends on the Core software version and is passed through untouched, so treat it as free-form diagnostic data rather than a fixed schema.