AwsSignatureHandler now overrides the synchronous Send() method in .NET 5.

[Timovzl]

fix: Synchronous HttpClient.Send().

AwsSignatureHandler now overrides the synchronous Send() method in .NET 5.

Closes #478.

I did not have time to conform to the contribution guidelines to the letter. Feel free to use this PR as you see fit. If you prefer to reject it and copy relevant changes to your own PR, I'm all for it.

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context.

Fixes # (issue)

Checklist

• I have squashed my commits into a single one with a message that aligns with the contributing guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[FantasticFiasco]

I think I'm done with the review. Do you have anything else to add or mention?

[Timovzl]

I think I'm done with the review. Do you have anything else to add or mention?

Great work, nice improvements. I've added one nitpick, but I have no further additions. I appreciate you picking this up so fast.