A maintenance script is needed that automatically scans images listed in the `mediamoderation_scan` table. This script should meet several requirements:
* It should be able to choose what files to process and/or prioritise based on the last time the file was scanned
* This should respect the API rate limits of PhotoDNA, or detect when limits are reached in determining whether a file has been scanned
* It should be reliable in getting an appropriately sized thumbnail of the file being scanned
* Any file that does not have a thumbnail and cannot be generated on-demand should be left for a future scan run
* Any errors or warnings in the maintenance script are properly logged
* An event be emitted to `statsd` when a check is performed for monitoring the number of requests to the API per wiki
* This script should email to a specified email address if a file is determined to be a match (T351407)
This will replace the existing maintenance script so that it can be easily run automatically.
=====Acceptance criteria
[] Ensure the requirements for the maintenance script are met
[] Ensure the maintenance script is well tested