ProtonDrive cloud support

[GertVanKruiningen]

Hi I would love to see support to connect to the new cloud source ProtonDrive by the Swiss company https://protonmail.com/
Their new product ProtonDrive looks amazing basically for its security features, so would be good to step away from the big ones like DropBox, the one I am currently using

Cheers
Gert

[perry-mitchell]

@GertVanKruiningen Some year or so ago I would probably consider adding new options like this, as it bridges Buttercup for a lot of potential users. Onboarding new services is hugely expensive in terms of our time, and I would ask that someone implements it in the core library as a PR if they want it supported elsewhere. I would approve ProtonDrive if:

• several people show interest
• someone submits a PR

Otherwise I'm afraid we'd avoid adding it for now. I'll move this to our admin repo for speculation.