How would this feature be useful?

It would be great to support mamba, which is a conda replacement solver that is dramatically faster. A solve of a complex package like ROOT (which is a reason to use conda in the first place) takes several minutes with conda, and a few seconds with mamba.

Describe the solution you'd like

Option 1: Provide a new backend: "mamba". This would simply make conda_install(...) use mamba instead of conda. This is the best option I could think of.

Option 2: Automatically use mamba if available over conda. This is slightly too magical, and there are minute difference in the solve (that shouldn't matter).

Option 3: Add a setting to select the command used for conda. I don't think there is a good reason to generalize too much - mamba is a drop-in replacement for part of conda (other parts can just use conda, as it's always available with mamba).

This was mentioned in #346 (comment) as a side note, but never attempted.