Feature/improve arn parsing and IAM Policy testability

[PeterKneale]

• I noticed SnsPolicy.cs was using regex to parse the source ARN instead of using Amazons supplied ARN.Parse(..) method.
• Before changing this I separated the two responsibilities of generating and applying the policy
• This allowed me to add an approval test against the IAM policy generated
• Then I made the actual change and introduced ARN.Parse(..) and observed no regressions.
• I also added a mechanism to validate the ARN I saw elsewhere.

[PeterKneale]

Is this sort of small improvement okay to add without a ticket - Please let me know if I overstep :)

[codecov]

Codecov Report

Merging #1080 (967198c) into main (e74693d) will increase coverage by 1.30%.
The diff coverage is 97.50%.

@@            Coverage Diff             @@
##             main    #1080      +/-   ##
==========================================
+ Coverage   84.80%   86.11%   +1.30%     
==========================================
  Files         135      136       +1     
  Lines        3298     3299       +1     
==========================================
+ Hits         2797     2841      +44     
+ Misses        501      458      -43     

Flag	Coverage Δ
linux	86.11% <97.50%> (+1.30%)	⬆️
macos	52.58% <97.50%> (+0.86%)	⬆️
windows	52.95% <97.50%> (+1.23%)	⬆️

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

Impacted Files	Coverage Δ
...c/JustSaying/AwsTools/MessageHandling/SnsPolicy.cs	0.00% <0.00%> (ø)
...aying/AwsTools/MessageHandling/SnsPolicyBuilder.cs	100.00% <100.00%> (ø)
...ng/Middleware/ExactlyOnce/ExactlyOnceMiddleware.cs	77.77% <0.00%> (-14.82%)	⬇️
src/JustSaying/JustSayingBus.cs	95.80% <0.00%> (ø)
src/JustSaying/Fluent/TopicPublicationBuilder`1.cs	83.72% <0.00%> (ø)
...rc/JustSaying/Fluent/TopicSubscriptionBuilder`1.cs	86.56% <0.00%> (ø)
...ing/AwsTools/QueueCreation/ServerSideEncryption.cs	100.00% <0.00%> (ø)
...AwsTools/MessageHandling/Dispatch/MiddlewareMap.cs	85.18% <0.00%> (ø)
...nt/PublishConfig/StaticPublicationConfiguration.cs	95.23% <0.00%> (ø)
...t/PublishConfig/DynamicPublicationConfiguration.cs	100.00% <0.00%> (ø)
... and 2 more

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[PeterKneale]

I can do the same for SqsPolicy if desired

[slang25]

Nice!

[slang25]

Thanks for this @PeterKneale, these improvements are always appreciated 🙂. We don't mind skipping issues when there isn't a design discussion to be had.