Allow adding user to cirun resource access

[aktech]

See https://github.com/conda-forge/conda-smithy/issues/2194 (and https://github.com/conda-forge/.cirun/pull/25#issuecomment-2548663553)

After the above is implemented, we need to call the conda-smithy cli with something like --cirun-users to be able to allow adding user to cirun resources, so that pull requests like these: https://github.com/conda-forge/.cirun/pull/25 can be automatically created by @cirun-bot when admin requests calls conda-smithy with this param, which in turn passes it to cirun client.

cc @jaimergp