make order of headers repeatable

[grubberr]

Signed-off-by: Sergey Chvalyuk grubberr@gmail.com

Closes #

Checklist

• Added docstrings and type annotations
• Added test coverage
• Updated changelog to describe any user-facing features or changed behavior

[codecov-commenter]

Codecov Report

Merging #474 (3d5f55d) into master (71ea521) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #474   +/-   ##
=======================================
  Coverage   98.75%   98.76%           
=======================================
  Files          18       18           
  Lines        1290     1291    +1     
  Branches      185      186    +1     
=======================================
+ Hits         1274     1275    +1     
  Misses          8        8           
  Partials        8        8           

Impacted Files	Coverage Δ
requests_cache/cache_keys.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 71ea521...3d5f55d. Read the comment docs.

[JWCook]

Looks like this fixes a regression bug; previously headers were correctly sorted (via normalize_request()), but I see that converting those to a set in get_matched_headers() means the order wasn't guaranteed anymore. Thanks for fixing that!

Looks like there's just one minor complaint from black, and a type warning from mypy. And could you also add a unit test that covers this?

[JWCook]

Updated and merged. This is included in the latest release (0.9). Thanks for the contribution!