Allow an issue to have absolute manual article ordering, instead of grouping them by Article Section

[pgoussy]

Is your feature request related to a problem? Please describe. Janeway's current method of ordering articles in an issue--i.e., displaying each Article Section in the order that they appear in the Section Manager, and displaying all articles within that section in the ordained order--isn't ideal for all journals.

For instance, PTPBio is a rolling publication that just has a single volume for the whole year, and they add articles throughout the year. Currently, that volume page lists all of the Research Articles, followed by all of the Special Issue articles. They would prefer that those articles display on the TOC in order of publication, regardless of whether they're categorized as a Research Article or a Special Issue.

For another example, for GS 1.1, Janeway currently displays the articles in Section order: all of the Letters, followed by all of the Research Articles, followed by all of the Short Essays, etc. However, in the print edition of this issue, these articles were displayed in a completely different order--it was divided into issue-specific groupings based on theme/subject, and within each of those groups, you might find articles of multiple different types (some Research Articles, some Short Essays, etc.). So not only are the articles not appearing in the same order as the print edition, there's also no way to render the issue-specific section titles on the Janeway TOC (unless we sacrifice the article types currently identified in the Article Section field).

Describe the solution you'd like In short: most journals have been treating the Article Section field less as a way of organizing an issue, and more as a tool for labeling the type of each individual article. We would like to stop using Article Section as the default organizational structure for issues, but we'd still like each article's assigned Section (that is to say, its "type") to be easily identifiable. Per our discussion on Discord several months ago, there are a few separate features that would need to be developed in order to achieve this.

This ticket is specifically for absolute article ordering: we would like to be able to dictate the absolute article order using the Article Number field on the import spreadsheet, OR by manually dragging-and-dropping on the Issue Management page, regardless of Article Sections

See also: #3080 #3081