fix(aws-api-mcp-server): origin header parsing

[arnewouters]

Fixes

Summary

Changes

Please provide a summary of what's being changed

The Origin header syntax is <scheme>://<hostname>:<port> so the logic we use for removing the port number by splitting on : and taking the first element is wrong.

• Fix parsing according to the Origin header syntax
• Update tests to also be in line with the correct Origin header syntax

User experience

Please share what the user experience looks like before and after this change

Checklist

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• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Is this a breaking change? (Y/N)

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.51%. Comparing base (b27ba88) to head (526251d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1851      +/-   ##
==========================================
+ Coverage   90.42%   90.51%   +0.09%     
==========================================
  Files         851      745     -106     
  Lines       63315    56411    -6904     
  Branches    10253     9357     -896     
==========================================
- Hits        57252    51060    -6192     
+ Misses       3772     3238     -534     
+ Partials     2291     2113     -178     

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