Update tile server config and reload somehow

[ray-millward-tessella]

We need to work out how to update the tile server config file to serve a new layer and reload whilst the site is running. Need to investigate if tileserver-gl can watch the config file or has a reload mechanism - ultimately could work how to restart the tile container.

Ultimately we can watch the tile layer folder with a cron job and restart the container if a new file appears. This will need a mechanism to know when a file was added.

Acceptance criteria:

• [x] The tile server can be restarted when the config changes.

[ray-millward-tessella]

I've updated the tile server image to include a script that watches for a trigger file. When the API updates the trigger file then it causes the tile server to reload by sending the appropriate signal.

[colin-turner-cg]

Terminal output after adding a new overlay file to my local Blob storage and sending an API query to trigger a model process: