Implemented a much-needed Setup() function for providers to implement,
which (as demonstrated in the backblaze provider) allows for
authentication in advance of needing to make calls to remote locations.
This could also be used to create a directory or perform some other
sanity check required for the provider to work. So far, haven't noticed
any performance impacts from this approach, besides not needing to auth
each time we make a request.
Should offer some speed boost, copying the file contents rather than
reading it all to memory then writing it back out. Should theoretically
be able to handle larger files as well, although some benchmarks
are TBD around filesize limits.
Expanding this as we go, currently have POC Backblaze B2 support and
basic 'disk' provider as well. Still WIP, but functional for the most
part. Also moving to simplified YAML configuration.
Overall, simplifying things to be extensible down the line. Still work
to be done, but coming along nicely.
