Use rattler_config crate

[pavelzw]

we could read the maximum concurrency from there: https://github.com/conda/rattler/blob/249ee2cda39a6250ff130788460e2485fd36c427/crates/rattler_config/src/config/concurreny.rs#L36 and https://github.com/conda/rattler/blob/249ee2cda39a6250ff130788460e2485fd36c427/crates/rattler_config/src/config/concurreny.rs#L19-L21

as well as s3 configuration.

also, we can move our config to this file

[pavelzw]

if we integrate conda/rattler#1480, we could also rework the whole configuration file and make it just read a pixi configuration file (with some extra config)

[justacec]

Seems to me that this application's intention is to focus on mirroring a repository which is independent of any particular local package management infrastructure. By using a specific package managers config file system, would that be requiring this application's users to use only that package manager? I ask because I am currently using conda and did not have the intention of shifting to pixi. (at least not right now)

[pavelzw]

you don't need to switch to pixi, just have a pixi-compatible config.toml lying around somewhere. this doesn't have anything to do with pixi technically.
i only want to use rattler-config for being able to reuse the code for configuring