4478: Surface the checksum in API and dkan:dataset-info

[paul-m]

Fixes #4478

Refresh of the #4642 PR.

Describe your changes

Enables LOCAL_URL_PERSPECTIVE to inherit the checksum from LOCAL_FILE_PERSPECTIVE.

We really should get rid of LOCAL_URL_PERSPECTIVE altogether, but this is a more minimal change.

% ddev drush dkan:dataset-info 95f8eac4-fd1f-4b35-8472-5c87e9425dfa      
{
    "latest_revision": {
        "uuid": "95f8eac4-fd1f-4b35-8472-5c87e9425dfa",
[...]
        "distributions": [
            {
[...]
                "file_path": "public:\/\/resources\/6e5a8b0e5f9ae95d1e239844aaab2db4_1767909623\/Asthma-Prevalence-Map-2017.csv",
                "file_checksum": "504180d7a251b915e5494bc48690dd6d",
[...]
            }
        ]
    }
}

QA Steps

• Add manual QA steps in checklist format for a reviewer to perform. Be as specific as possible, provide examples if appropriate.

Checklist before requesting review

If any of these are left unchecked, please provide an explanation

• I have updated or added tests to cover my code
• I have updated or added documentation

[paul-m]

Needs tests.
Needs testing steps.