Lots of broken links in the episode table docs

[dstansby]

In the docs at https://ohdsi.github.io/CommonDataModel/cdm54.html#episode in the ETL Conventions columns, there are a few broken links that simply say "[article]" instead of hyperlinking out to other pages.

[asharaali]

I went looking for the source of these so I could fix them, and ran into a problem worth reporting before anyone writes a patch: for most of them there is no page to link to.

The text comes from two CSVs that site/cdm54.qmd renders. Four are bare placeholders with no URL at all, in inst/csv/OMOP_CDMv5.4_Field_Level.csv:

• episode.episode_concept_id — "Please see [article] for cancers and [article] for non-cancers describing how these are defined."
• episode.episode_start_date — "Please see [article] for how to define an Episode start date."
• episode.episode_end_date — "Please see [article] for how to define an Episode end date."
• episode.episode_number — "Please see [article] for the details of how to count episodes."

The fifth is in inst/csv/OMOP_CDMv5.4_Table_Level.csv on the episode row, and it is a real link — but it is also broken, in a way that isn't visible from the rendered page. It points at https://ohdsi.github.io/OncologyWG/model.html#Episodes, capital E. The heading on that page is <div id="episodes">, lowercase, so the fragment doesn't resolve and the link drops you at the top of the page. That one is a one-character fix.

The other four are the harder part. Checking the OncologyWG model page for the content they promise:

• The Episodes section is still marked "Under Construction" and the concept-class list under it is a literal -TODO-.
• There is nothing on that page about how to define an episode start date or end date, and nothing about counting episodes.
• There is nothing about non-cancer episodes anywhere on it. That is expected given the page's scope, but it means the "for non-cancers" half of the episode_concept_id sentence has no candidate target at all.

The one place with real content is the OncologyWG wiki's EPISODE page, which does give start- and end-date rules, though per episode type rather than as one general rule — e.g. Episode of Care starts at the first recorded condition excluding unconfirmed rule-outs and has no end date unless the patient dies; Disease Dynamic ends at the start of the next Disease Dynamic or Treatment episode.

So this isn't only a link-fixing job. Deciding what the ETL Conventions should point implementers at is a convention decision, and I'd rather not guess it on the episode fields. Two questions:

1. Should these point at the OncologyWG wiki rather than the model site? The Table_Level row currently points at the site, so the two would disagree unless both move.
2. Is there a source for non-cancer episode definitions that I'm not finding, or should that clause be dropped until one exists?

Happy to open the PR once those are settled. The anchor-case fix on the Table_Level row is independent of both and I can send that on its own if it's useful.