Implement deletion by prefix API about uplink

[egonelbre]

Is this deletion by prefix or multiple objects.

For deletion by prefix we can implement a separate func, however, for deleting multiple objects we may want to consider a batching API that also supports renames, deletes, downloads etc.

[mniewrzal]

I don't remember exactly for which functionality we added this TODO point while doing MPU API. I agree with what you wrote also I don't plan to work on this actively until we will have real use cases e.g. performance issues.

[egonelbre]

Given storj/storj#4256, I think delete by prefix is a reasonable feature.

[mniewrzal]

Sounds good. I changed the title to reflect intention.

[kaloyan-raev]

Such an API would help in a few use cases:

• Implement rclone purge.
• Improve uplink rm --recursive. Currently, it lists the prefix and deletes the object one by one.
• Any app that emulates folders with prefixes.

[egonelbre]

One thing to consider is that we probably want to give feedback to the caller on the progress. Otherwise, it might seem like the API call has gotten stuck.

There are two approaches that come to mind:

A. Add DeleteByPrefix with a Limit. The Limit (e.g. max 1000) is enforced by the satellite, and it will respond with the number of deleted objects. This has the added benefit that there's some uplink rate limiting happening for the calls.

B. Add streaming rpc DeleteByPrefix which every N deletes sends an update to the satellite.