fix: use SDK AppID for User-Agent

[ThirdEyeSqueegee]

Issue #, if available:
N/A

Description of changes:
The old User-Agent middleware logic was bugged causing the provider and add-on versions to not show up in service logs. This was due to our custom middleware adding an entirely new header instead of modifying the existing UserAgent header which was never ingested on the service side.

• Use the SDK's middleware import to fix this

Example of UserAgent after this change (from service log):

UserAgent=aws-sdk-go-v2/1.39.0 ua/2.1 os/linux lang/go#1.24.12 md/GOOS#linux md/GOARCH#amd64 api/secretsmanager#1.39.4 app/secrets-store-csi-driver-provider-aws-2.1.0 m/E,z

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 61.56%. Comparing base (6dbe3b9) to head (6a8bd60).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
credential_provider/irsa_credential_provider.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #556      +/-   ##
==========================================
+ Coverage   60.10%   61.56%   +1.46%     
==========================================
  Files          11       11              
  Lines         762      752      -10     
==========================================
+ Hits          458      463       +5     
+ Misses        287      274      -13     
+ Partials       17       15       -2     

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[i-am-SR]

Please add some info reg the bug in the old User-Agent middleware logic.

[derik01]

Could we explore using AppID for configuring the user agent: https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/config

[simonmarty]

Could we explore using AppID for configuring the user agent: https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/config

Maybe, as long as it doesn't risk getting overwritten too easily by accident by customers.

[ThirdEyeSqueegee]

Pivoted to using AppID a couple commits ago @simonmarty. Plz review whenever you can 😁

[derik01]

Cursory look suggests that using AppID does what Angad was proposing in a earlier revision: https://github.com/aws/aws-sdk-go-v2/blob/de58dc6cdc4c35ac4687d53cff781a6027a0f52f/codegen/smithy-aws-go-codegen/src/main/java/software/amazon/smithy/aws/go/codegen/AwsClientUserAgent.java#L79-L91

[i-am-SR]

The implementation has changed since the last review. Please ensure we have validated the updated UA value in the service logs.

[simonmarty]

Experiencing some weirdness with the IRSA integ tests failing to create EKS clusters. I'm going to override the approvals.