Add support for more than 10K SAS tokens for file uploads or optimize token usage
Currently we have file uploads from devices through IoT Hub. For each upload the device has to receive a SAS token that is valid for a minimum period of 1 hour. Storage supports up to 10000 SAS tokens issued at the same time, which effectively limits the number of devices doing uploads to 10K. For use cases where for example you have 30K devices and every device has to do an upload every half an hour this doesn't work.
1) Add ability to link multiple storage accounts to file uploads on IoT which would allow to at least scale by 10K for each storage.
2) Add ability for devices to manually expire the token. Device gets a token, does the upload and invalidates the token so that it is returned to available tokens "pool" for other devices to use.