Add analog downscaling prototype

[dgergel]

This PR adds the analog-inspired, quantile-preserving downscaling method as a new service. It is split up into two services, train_aiqpd and adjust_aiqpd and is based on the implementation of QDM. This is intended to supersede spatial disaggregation as the main mode of downscaling in dodola for the time being.

Basic CLI interface is:

dodola train_aiqpd /path/to/coarse_reference.zarr \
/path/to/fine_reference.zarr 
--out /path/to/trained_afs.zarr \
--v "tasmax", 
--k "+"

dodola apply_aiqpd /path/to/biascorrected.zarr \
/path/to/trainedafs/zarr \
-- year 2026
 --v "tasmax" 
--out /path/to/trained_afs.zarr \

closes #73

[brews]

This is cool, @dgergel. I'm pumped to see how this scales.

I have a few inline comments and corrections — as you can see.

In addition:

• Add this change to HISTORY.rst. Cite this PR and include your github username.
• Could we squeeze in at least one service.py-test to cover new behaviors/services? I think it'd be fine moving/adapting the core.py tests to fill this gap, if you don't want to write something new (because if service.py is tested, then core.py is tested). But I think we need test coverage for those new services.
• In dodola/tests/test_cli.py could you add train-aiqpd and apply-aiqpd to the test_cli_helpflags test. The IDs for this would be train-aiqpd --help and apply-aiqpd --help, respectively.

[dgergel]

@brews tests are passing, this is ready for another review!

[brews]

Thanks! I have a few other quick changes needed! I'll talk with you about setting up tests.

[dgergel]

@brews I updated the raise statement and noted the test changes we talked about in #113 for a follow-up PR. I think this might be ready to merge.

[dgergel]

@brews spoke too soon. I need to make a couple updates now that we're pulling from my updated branch of xclim with the edge cases fixed.

[brews]

@dgergel Okay! Appreciate the heads up!

[dgergel]

@brews okay now it's actually ready!

[brews]

For the record it looks like this is running with https://github.com/ClimateImpactLab/xclim@add_analog_downscaling. The commit hash is c5507ba29c19f957270789fd790ffe6c315a3daa.

[brews]

This has all the changes I requested. Thanks!

We're going to want to be sure to pin this new xclim to a commit hash or tag before the next release.