Draft: BlobStore (DataStore 3rd attempt)
Replaces !265 and !261 (merged)
DataStore has been renamed BlobStoreInterface so it's clear it's a trait not concrete type, and it's only about blobs not about message archive and such. It's in the store::blob
module so we can add other stores in the future.
TODO
- update MR description
- update docs
- update changelog