feat: RocksDB implementation for File Manager

[a-moreira]

Adds a RocksDB implementation for File Storage.

Next steps in a new PR:

• Refactor Errors
• Refactor FileStorage and FileDataTrie interfaces to allow:
  • batch inserting and retrieval.
• Use concrete types for StorageDb, ditch the Backend trait and thus avoid locking access (RwLock) within the File Manager.

[snowmead]

I would rather we simplify the trait api to only include a single insert method. Right now we have insert_file and insert_file_with_data.

IMO we want to abstract away the internal logic and architecture of the file manager from services and tasks. Do you think we could have only an insert_file fn (which does not force services and tasks to create a preliminary trie with FileDataTrie to finally call insert_file_with_data)?

[ffarall]

I agree this would help making things less confusing, but you'd have to be careful that you can still serve the use case of the RPC of user uploads file, and the BSP receives file handler that gets chunk by chunk.

[snowmead]

Good job overall!

Probably most of the comments I left could be put as TODOs, but I think there is some work to
do on the structure of file manager and file trie.

[ffarall]

I agree this would help making things less confusing, but you'd have to be careful that you can still serve the use case of the RPC of user uploads file, and the BSP receives file handler that gets chunk by chunk.