Support ISSN in chapter processed book metadata
Context
We have some existing chapter processed books that have an ISSN in book metadata.
Proposal
Support this field so we can continue to index and display it on Bookshelf and related sites.
See: https://www.ncbi.nlm.nih.gov/books/NBK378971/
Implementation
Use <issn></issn>
as described in the BITS docs here, as shown in the example below:
<book-meta><book-id book-id-type="pmcid">cadthetb</book-id><book-title-group><book-title>CADTH Issues in Emerging Health Technologies</book-title></book-title-group><pub-date date-type="pubr" publication-format="print"><year>2016</year></pub-date><issn>1488-6324</issn><publisher><publisher-name>Canadian Agency for Drugs and Technologies in Health</publisher-name><publisher-loc>Ottawa (ON)</publisher-loc></publisher><permissions><license license-type="open-access" xlink:href="https://creativecommons.org/licenses/by-nc-nd/4.0/"><license-p>Except where otherwise noted, this work is distributed under the terms of
a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
licence (CC BY-NC-ND), a copy of which is available at <ext-link ext-link-type="uri" xlink:href="https://creativecommons.org/licenses/by-nc-nd/4.0/">https://creativecommons.org/licenses/by-nc-nd/4.0/</ext-link></license-p></license></permissions><abstract><!-- https://www.cadth.ca/issues-emerging-health-technologies --><p>Issues in Emerging Health Technologies is a series of concise bulletins describing
drug and non-drug technologies that are not yet used (or widely diffused) in Canada;
in most cases, Health Canada’s approval is anticipated in the next six to 18 months.
Bulletins include a description of the emerging technology, patient indications,
regulatory status, adverse effects, costs, anticipated diffusion rates,
implementation issues, and a discussion of the reliability and quality of available
evidence. While the bulletins analyze all available data, the evidence base is
generally insufficient to permit a meta-analysis of individual trials or other
statistical analyses. Each bulletin is peer-reviewed by two or more external
clinical experts.</p></abstract><custom-meta-group><custom-meta><meta-name>books-source-type</meta-name><meta-value>Database</meta-value></custom-meta><custom-meta><meta-name>books-subject</meta-name><meta-value>Health Care</meta-value></custom-meta><custom-meta><meta-name>books-subject</meta-name><meta-value>Evidence-based Medicine</meta-value></custom-meta></custom-meta-group></book-meta>