This API fulfills the purpose to save and retrieve the state of the VersionedItemsTable control.
It just implements a simple in memory list to store the items (that's why we call it dummy).
The more interesting part is the authentication respective validating the Authorization Bearer Token, which will be the Extension's App Token generated by Azure DevOps.
To build the Rest API you need Docker to be installed.
dummyrestapi> docker build -t dummyrestapi .
To run it you need to pass the Extensions Secret as an environment variable. The most simple setup is to run the docker container locally and open a tunnel via ngrok and enter the https ngrok tunnel adress as the endpoint URL in the control settings.
Run the container:
docker run -e 'extension_secret=<extension secret from portal>' -p 5001:80 dummyrestapi
Open the ngrok tunnel:
ngrok http 5001
To retrieve the extension secret you must go to the management pane of your Visual Studio Marketplace account: