Generating links for sections of the CFR that don't follow the common pattern

[peregrinator]

We're using the GPO link service to direct users to the latest published PDF for a particular section of the CFR.

So for a CFR reference of 43 CFR 3170.4 we would generate a link like https://www.govinfo.gov/link/cfr/43/3170?link-type=pdf&sectionnum=4. This is the standard case and works as expected.

However there are titles in the CFR that don't follow this pattern and we're currently unable to generate a link to the PDF using the link service. For example: https://ecfr.federalregister.gov/on/2020-08-03/title-43/subtitle-B/chapter-II/subchapter-C/part-3170?toc=1

Here the title is using subparts to group the content in a way that we would usually expect parts to be used. So section 3175.10 is actually in part 3170 (instead of 3175 as we'd usually expect). This means that when we create the link service url using the part the section actually exists in, https://www.govinfo.gov/link/cfr/43/3170?link-type=pdf&sectionnum=10, we get an error. If we substitute the subpart for the part then we get the correct PDF, https://www.govinfo.gov/link/cfr/43/3175?link-type=pdf&sectionnum=10.

So while the PDF exists and is accessible with the right combination of parameters it's more difficult to generate automatically because it doesn't follow the common pattern. The correct solution here may be a bit hard as it seems like it may require larger changes to parameters but I wanted to start the conversation.

Thanks!

[jonquandt]

@peregrinator -- this one appears to be down to the structure of the CFR itself. We will have to do some additional investigation to see if there are additional parameters or tweaks to our link service to make these more accessible. This isn't a short-term fix, unfortunately, and we'll likely need discuss with other folks offline.