Update Device Command

Adds one or more commands in a JSON array of dictionaries for the device of the specified account. When the device requests commands the next time, they will be sent from the queue once and then be deleted.

Example Payload:

[
    {
      "message": {
        "msg": "Hi there, this is my name.",
        "level": 4,
      },
      "platform": "ros",
      "topic": "/rosout_agg",
      "type": "rosgraph_msgs/Log",
      "expiration_secs": 100,
      "repeat": {
        "rate": 4,
        "length": 5,
        "cancel_on_next_message": true
      }
    }
  ]

The maximum text length of an individual command should be 300 KB including all encoding

For the first command message you send on a topic, Mission Control will wait until there is at least a subscriber on that topic before sending the message and adds slightly more padding time after the first one for any stragglers which take a little while. This usually means it takes 1-2 seconds before it triggers the first command on that topic. Otherwise, the messages would be lost. After this, it is immediately delivered. (This is a constraint of ROS, not Mission Control)