API: Get assets assigned to assets

[echristley]

Server (please complete the following information):

• v5.1.8 build 6148 (g3ca3de9e4)
• OS: Ubuntu
• Web Server: Apache
• 7.2.24-0ubuntu0.18.04.8

Is your feature request related to a problem? Please describe.
We're using Snipe-IT to control test equipment that is integrated with multiple teams. We have written Jenkins libraries that allow a test run to check out a device, run tests using that hardware, and then check it back in. This allows us to share a stable of test hardware between multiple teams, instead of each team having their own stable that sits idle the majority of the time. We have set up custom fields that we can retrieve via the API that provides the tests with all the info they need to manipulate the device.

The immediate issue we're running up against is that we would like to associate a network power switch with a device, so that a test could remotely power cycle the device. I can create the power switch as an asset, and then check it out to the device; however, the API to retrieve info for a device does not include a list of assets that it has checked out. From the API perspective, there does not appear to be a way to determine what assets an asset has checked out.

Describe the solution you'd like
It would be helpful for the GET method of the device endpoint to include a list of device ids of assets that the device has checked out.

Describe alternatives you've considered
A search like "assets checked out to " would also work. Really, any method to discover the associated asset would be just fine.

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