adding unit and name attributes to layers

[prayner]

addresses #16

---

Description

Checklist

Please confirm that this pull request has done the following:

• Tests added
• Documentation added (where applicable)

Notes

[lewisjared]

I think we need to add the required attributes to the total as well as the layers in the sum_layers function.

We should also add a test to the test_om_prior.py which verifies that the units are in the output. This helps to ensure that they don't get lost if we do further changes. This one is a bit annoying because it requires running the whole workflow to test this so it can be a bit slow.

A simple test like this could be sufficient for now:

def test_required_attributes(output_domain_xr):
    assert output_domain_xr.variables["OCH4_TOTAL"].attrs == {
        "units": "kg/m^2/s",
        "long_name": "OCH4_TOTAL",
    }
    assert output_domain_xr.variables["OCH4_WETLANDS"].attrs == {
        "units": "kg/m^2/s",
        "long_name": "OCH4_WETLANDS",
    }

This currently fails until the fix to the total has been implemented.

We should have a session on how to run pytest and the test suite.

[prayner]

added the attributes, I'll leave the test to someone who understands pytest

[lewisjared]

@prayner Are you able to see any line-specific comments or are they not available in emacs?

[prayner]

Don't think I can see them in emacs ... let's see if the gh cli reveals them

[prayner]

I'm not seeing in-line comments, are there some here?

[lewisjared]

Ok good to know.

For constants, "SCREAMING_SNAKE_CASE" is the preference. If we don't change this as part of this PR it will likely later be cleaned up.

I had another comment to use setncatts to set all the values at the same time instead of looping.

I'll fix them up with the tests

[lewisjared]

@prayner Can I add the tests to this branch? If so please assign this PR to me