[PR #9333/2ac962cc backport][3.10] Small cleanups to connector ConnectionKey usage

[patchback]

This is a backport of PR #9333 as merged into master (2ac962c).

What do these changes do?

• Add some missing typing
• Reduce some indent
• Reduce some dict lookups

Are there changes in behavior for the user?

no

Is it a substantial burden for the maintainers to support this?

no

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.79%. Comparing base (b959358) to head (afa0ff1).
Report is 1 commits behind head on 3.10.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             3.10    #9338      +/-   ##
==========================================
- Coverage   97.79%   97.79%   -0.01%     
==========================================
  Files         108      108              
  Lines       34885    34883       -2     
  Branches     4173     4173              
==========================================
- Hits        34115    34113       -2     
  Misses        573      573              
  Partials      197      197              

Flag	Coverage Δ
CI-GHA	97.68% <100.00%> (-0.01%)	⬇️
OS-Linux	97.36% <100.00%> (-0.01%)	⬇️
OS-Windows	94.97% <100.00%> (-0.01%)	⬇️
OS-macOS	97.06% <100.00%> (-0.01%)	⬇️
Py-3.10.11	96.92% <100.00%> (-0.01%)	⬇️
Py-3.10.15	96.86% <100.00%> (-0.01%)	⬇️
Py-3.11.10	96.94% <100.00%> (-0.01%)	⬇️
Py-3.11.9	97.00% <100.00%> (-0.02%)	⬇️
Py-3.12.6	97.40% <100.00%> (-0.01%)	⬇️
Py-3.13.0-rc.2	97.39% <100.00%> (-0.01%)	⬇️
Py-3.8.10	94.37% <100.00%> (-0.01%)	⬇️
Py-3.8.18	96.66% <100.00%> (-0.01%)	⬇️
Py-3.9.13	96.84% <100.00%> (-0.01%)	⬇️
Py-3.9.20	96.78% <100.00%> (-0.01%)	⬇️
Py-pypy7.3.16	96.38% <100.00%> (+<0.01%)	⬆️
VM-macos	97.06% <100.00%> (-0.01%)	⬇️
VM-ubuntu	97.36% <100.00%> (-0.01%)	⬇️
VM-windows	94.97% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.