Cloud-first FMS branch should be backwards compatible

[pgarrison]

As currently designed, the cloud-first FMS features will cause breakages if used with the pre-cloud-first FMS ETL pipeline. But the cloud-first FMS ETL pipeline changes will cause breakages if used with the pre-cloud-first BFF. To enable a smooth migration, the BFF features should all be backwards compatible.

This is because the file_path is now the cloud path, which will break key features like opening a file in a viewer or downloading a file.

With this backwards compatibility, the following migration is possible.

1. Announce the new BFF version, and give people some time (a day?) to download it.
2. Deploy the ETL changes.

Without this backwards compatibility, we might have to accept that BFF will temporarily be broken for internal users.

[pgarrison]

This would look like adding a bunch of feature detection conditionals to the code from #370, #376, and #377.

if (file has a "Should Be In Local" annotation) {
     do the new behavior
} else {
     do the old behavior
}