fix(commons): keep AWS_SDK_UA_APP_ID idempotent and <=50 chars

[saschabuehrle]

Fixes #5082

This patch makes commons user-agent app-id initialization safe for repeated module loads and compliant with the AWS SDK 50-char limit:

• avoid appending the PT/NO-OP marker when it already exists
• cap the final AWS_SDK_UA_APP_ID value to 50 chars
• add regression tests for idempotency and max-length behavior

Greetings, saschabuehrle

[boring-cyborg]

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[dreamorosi]

Although I don't have a better solution yet - which is why we haven't addressed the issue - I don't think trimming, slicing, and generally doing all these operations every time the module is imported is the way to go.

I'd rather help customers address the root cause of why the module is imported twice - which is bad regardless of the UA length - or give a way to opt out from UA concatenation altogether.