Lots more cleaning up

[gwynne]

• Bump the swift-http-types version requirement
• Fix a broken link in the README
• Add a dependency on stairtree/async-helpers
• Do lots of general cleanup of syntax and formatting
• Improve documentation comments
• Use the locking primitives from AsyncHelpers
• Provide better granularity of request timing when trace logging
• Remove archaisms around the Concurrency support

[codecov]

Codecov Report

Merging #11 (4b0ccc8) into main (6d3efe8) will increase coverage by 0.49%.
Report is 1 commits behind head on main.
The diff coverage is 49.15%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
+ Coverage   57.34%   57.84%   +0.49%     
==========================================
  Files          12       10       -2     
  Lines         211      204       -7     
==========================================
- Hits          121      118       -3     
+ Misses         90       86       -4     

Files	Coverage Δ
Sources/StructuredAPIClient/NetworkRequest.swift	0.00% <ø> (ø)
...s/StructuredAPIClientTestSupport/TestRequest.swift	100.00% <100.00%> (ø)
...cturedAPIClientTestSupport/TestTokenProvider.swift	80.00% <ø> (ø)
...StructuredAPIClientTestSupport/TestTransport.swift	89.47% <100.00%> (ø)
...uredAPIClient/Handlers/AddHTTPHeadersHandler.swift	95.00% <66.66%> (-5.00%)	⬇️
...PIClient/Handlers/TokenAuthenticationHandler.swift	72.09% <77.77%> (-3.91%)	⬇️
Sources/StructuredAPIClient/NetworkClient.swift	83.78% <78.26%> (+1.64%)	⬆️
...turedAPIClient/Transport/URLSessionTransport.swift	0.00% <0.00%> (ø)
...rces/StructuredAPIClient/Transport/Transport.swift	40.00% <0.00%> (-40.00%)	⬇️
...ructuredAPIClient/Transport/TransportFailure.swift	0.00% <0.00%> (ø)

[tkrajacic]

LGTM

[0xTim]

LGTM