LTI-373: forward extra params from LMS to BBB on join,create

[Mariam05]

The Rooms app will check if any extra params are set in the broker for the current tenant. If they are, then the app will forward them to BBB on the join or create call, depending on what was specified in the broker.

The hash will look something like this:

{
  "settings": {
    "ext_params": {
      "join": {
        "custom_user_image": "ext_user_image"
      },
      "create": {
        "custom_context_id": "ext_course_id"
      }
    }
  }
}

Upon launch, the rooms app will check for the custom_params hash in the launch_params. It will then save the intersection of the keys from the custom_params hash and the ext_params retrieved from the broker in the 'settings' culumn of the room, under the key "ext_params".