[ActiveStorage] Adding Backblaze B2 as a a cloud storage service.

Backblaze B2 is 1/4 the price of AWS, and substantially cheaper than Google & Azure. They have a great API and 10 years in business, so they’re hardly underdogs any longer.

https://www.backblaze.com/b2/cloud-storage-pricing.html

Would be happy to see a Backblaze adapter for Active Storage. We’ve designed the adapter system with a similar intent as Active Record: A small number of adapters in the gem, but with an easy way to add additional adapters via supporting gems.

So please do investigate a Backblaze adapter as a separate gem. Thanks for working on this!