web workflow API endpoint to return free space on device

[vladak]

https://github.com/adafruit/circup code has a TODO to check free space on a device before installing a module. To support this for web workflow (adafruit/circup#156) as well, the value available needs to be available via the REST API.

[tannewt]

This would use f_getfree() internally. We may want to add it to the BLE workflow API too.

[Neradoc]

Free space (and total space) would be useful to show in the file list page too (or at least on cp.org via /code ?)
I don't know if we want the info to be in /cp/version.json or a separate url.

[makermelissa]

Free space (and total space) would be useful to show in the file list page too (or at least on cp.org via /code ?) I don't know if we want the info to be in /cp/version.json or a separate url.

From the code editor standpoint, I would think another (similar) URL would be better because the version stuff usually doesn't change much once the board is booted and it can be a bunch to parse through. Maybe something like /cp/diskinfo.json and then other filesystem stuff could go there unless it adds a lot of overhead and makes the CP too big.