Partner EPUB annotations not correctly associated with DOI

### Note
This came up previously with the same partner in https://github.com/hypothesis/product-backlog/issues/808 - though as far as I can tell, at one point it started to "just work" and we're not sure why it didn't initially work and what made it work in the end. Also not sure if we're seeing the exact same issue here— linking just in case.

Zendesk ticket is here: https://hypothesis.zendesk.com/agent/tickets/3926

### Summary
A partner has added some test annotations on an EPUB. The annotations can be retrieved using a `wildcard_uri` search, but not by searching for the DOI. It appears that the individual chapters of the book aren't correctly associated with the DOI.

### Background
The book is split up into chapters which exist at different URL fragments, e.g.,

- Landing page for book: https://www.ubiquitypress.com/site/books/10.5334/baj/
- Introduction: https://www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=Text%2F010_quist_book_Introduction-v4.html
- Chapter 1: https://www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=Text%2F010_quist_book_Chapter1.html
- Chapter 5: https://www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=Text%2F010_quist_book_Chapter5.html

If you look at the metadata for [the landing page](https://www.ubiquitypress.com/site/books/10.5334/baj/), you'll see the DOI in the ``:
``

Within the ereader on all of the chapter pages you'll also see the DOI in the ``:

``

I would expect the DOI to be associated with the landing page as well as all of the chapter pages, and therefore searching for the DOI would return annotations on the landing page and throughout the book. That is not the case.

### Example queries

`https://hypothes.is/api/search?wildcard_uri=https://www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=*` returns 3 annotations made on the EPUB:

- https://hyp.is/U3pAlDtLEemb6ct_pp-cRw/www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=Text/010_quist_book_Chapter5.html
- https://hyp.is/PMBiDDtLEemrYifnuptaxg/www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=Text/010_quist_book_Chapter4.html
- https://hyp.is/rAeWuDtAEemIOGsMUffNNQ/www.ubiquitypress.com/site/books/10.5334/baj/read/?loc=Text/010_quist_book_Chapter2.html

Same results come up using https://hypothes.is/search and the API.

However `https://hypothes.is/api/search?uri=doi:10.5334/baj` only returns an annotation made on the landing page for the book, and none of the annotations made within the book:

- https://hyp.is/VY5kBDtCEemGOoPoxNToUA/www.ubiquitypress.com/site/books/10.5334/baj/

Again, same results come up using https://hypothes.is/search and the API.

### My question

I _think_ the partner needs to make use of `` within the ereader.

What I'd like help with is:
1. Am I on the right track?
2. If so, what should `somevalue` be?

Start with the example EPUB chapter URLs, their head metadata, and the API queries for wildcard_uri and uri=doi:10.5334/baj. Compare how chapter and landing-page annotations are associated, then verify the expected behavior against the linked prior issue and Zendesk ticket. Done means the required metadata or implementation change is identified and DOI searches return the chapter annotations.

Written by the indexing model from the issue text.