Fix result retrieval issues

[abought]

🦑 Happy to break this up into >1 PRs. It represents a set of tweaks I made to support a particular demo use case.

Purpose

• Fix an issue where search result links could sometimes generate "subject not found" links for detail pages (due to mixing of not-inverse quote_plus / unquote operations)
  • This manifested when a search index subject id name contained spaces
• Improve handling of fields in DGPF
  • Explicitly document all three syntaxes that were supported previously, and the need to specify the special template fields explicitly in fields config
  • Fix mismatch between doc and project dependencies that prevented local doc build on Py3.13 (cgi module was removed, and old django versions used by docs tried to import it)
  • Add missing unit test for existing (field name, alias) mode
  • Allow (field_name, alias) mode to work with dotted path syntax (item.citation.title). Previously it only worked with top level keys. Now it can fetch a field that is inside a nested object
    • I did not update the get exact field name syntax for dotted paths, on the grounds that template variables shouldn't have . in the name

TODO

• On Monday I'll test this inside my own custom portal to verify functionality in a real world test case.
• Verify that doc dep changes work in CI for old versions of python (5 warnings exist but they predate this PR- see comments below)

[abought]

With new dependencies, the doc build is generating 5 warnings. But it seems those warnings were also being generated previously under old versions, eg this December CI run:
https://github.com/globus/django-globus-portal-framework/actions/runs/12320265953/job/34389140427

Might be a good idea to review known issues before merging, to make sure these aren't new breakages. I can brush up on my sphinx to dig in if needed.