Optimize Invalid command removal.

[JimBobSquarePants]

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• I have written a descriptive pull-request title
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Description

This PR does a few things

• Prevents multiple enumeration of comand keys and removes invalid commands in a single loop.
• Allows duplicate commands in the URL (avoiding ArgumentException), taking and parsing only the last one. (Duplicates are not counted in cache key generation as that happens following stripping)
• Update ImageSharp to v2.1.2

[codecov]

Codecov Report

Merging #268 (f8fdde6) into main (414abfe) will decrease coverage by 0%.
The diff coverage is 100%.

@@         Coverage Diff         @@
##           main   #268   +/-   ##
===================================
- Coverage    85%    85%   -1%     
===================================
  Files        75     75           
  Lines      2036   2029    -7     
  Branches    298    296    -2     
===================================
- Hits       1741   1735    -6     
  Misses      211    211           
+ Partials     84     83    -1     

Flag	Coverage Δ
unittests	85% <100%> (-1%)	⬇️

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

Impacted Files	Coverage Δ
...Commands/PresetOnlyQueryCollectionRequestParser.cs	100% <100%> (ø)
...Sharp.Web/Commands/QueryCollectionRequestParser.cs	71% <100%> (ø)
.../ImageSharp.Web/Middleware/ImageSharpMiddleware.cs	80% <100%> (-1%)	⬇️
.../Synchronization/RefCountedConcurrentDictionary.cs	72% <0%> (-4%)	⬇️
src/ImageSharp.Web/Commands/CommandCollection.cs	94% <0%> (+8%)	⬆️

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[brianpopow]

Looks good

[ronaldbarendse]

Allows duplicate commands in the URL (avoiding ArgumentException), taking and parsing only the last one. (Duplicates are not counted in cache key generation as that happens following stripping)

Can you elaborate how you'd get an ArgumentException, because the following query strings both work and will result in the same parsed commands:

• ?width=400&height=400&rxy=1,1
• ?width=400&height=400&rxy=1&rxy=1

This is because StringValues.ToString() joins multiple values as a comma separated string, resulting in the same 1,1 value for the rxy command, not duplicate commands. This is therefore a breaking change in how the command parsing works, as some users might depend on this behavior.

[JimBobSquarePants]

If someone depends on non supported scenarios then that’s their problem. I have no obligation to care.