Include issue + supp file DOIs in DOI manager

Currently, the DOI manager only displays article DOIs - including issue (and maybe even supp file) DOIs would make it easier to check DOIs statuses. (And poll for status en masse/attempt to re-register/troubleshoot more easily.) Currently, troubleshooting issue DOIs is tricky as it is hard to find any information about the deposit/response/status in the system.

(Checked in 1.5.1. across multiple journals - cannot see issue level DOIs in the manager.)

Currently, the only information I can find re: issues DOIs at all is in the issue manager:
Everything else is in the manager settings, but that doesn't really tell you anything about individual DOIs.

User story(ish):
Currently struggling with an issue DOI where the article DOIs in the issues are fine / registered okay - which is the first step for troubleshooting - but I cannot see anything else about this issue DOI or a response XML, which is complicating things a bit. I also cannot find anything in the documentation: https://janeway.readthedocs.io/en/latest/published/issues.html?highlight=issue%20doi#issue-dois

Start in the DOI manager and compare its current article-DOI display with the issue manager, which is the only place the issue describes as exposing issue DOI information. Review the linked issue-DOIs documentation and trace how deposit or response status is surfaced. Done should make issue DOIs, and any supported supplementary-file DOIs, discoverable with enough status information to troubleshoot them.