[Amazon.Lambda.RuntimeSupport] fix: Find header key with insensitive comparison

Issue

Idea for #2093

Changes

Looks up for headers without any case restrictions.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

The change looks good but can you rebase the PR to the dev branch? The PR has picked up some commits that are in master that haven't yet been backported back to dev.

Also the PR needs a change file to take care of change log and versioning. Can you add the following content, feel free to change the change log messages, in the following file: .autover\changes\<random-guid>.json

{
  "Projects": [
    {
      "Name": "Amazon.Lambda.RuntimeSupport",
      "Type": "Patch",
      "ChangelogMessages": [
        "Fix issue making HTTP header comparisons be case insensitive"
      ]
    }
  ]
}

Hey @normj,

Thanks for the review, I'll rebase from the dev branch and add a change log soon!

https://github.com/aws/aws-lambda-dotnet/actions/runs/16104625097

I rebased your changes on top of dev @duncanista

Hey @GarrettBeatty,

Thanks – sorry for taking a while, had a busy last week.

I appreciate the modifications!

running integration tests on latest commits https://github.com/aws/aws-lambda-dotnet/actions/runs/16121546157

hi @duncanista i ran the tests locally and it looks like the unit tests are failing related to the change. Amazon.Lambda.RuntimeSupport.UnitTests

are you able to take a look? looks like most of them have the same error message System.ArgumentNullException : Value cannot be null. (Parameter 'key')

@GarrettBeatty updated the code to instead of checking a key on every Get, now an internal case insensitive headers dictionary is generated during the constructor.

Let me know if this is better, it should pass now. Sorry for taking so long.

On another note, do you want me to add unit tests for the RuntimeApiHeaders file? There seems to be none, I know it's kinda trivial, but still.

thanks i will rerun your changes through the test pipeline tomorrow morning

< On another note, do you want me to add unit tests for the RuntimeApiHeaders file? There seems to be none, I know it's kinda trivial, but still.

I think the other tests cases probably cover RuntimeApiHeaders indirectly, but if you would like to add more test cases feel free. I will approve it in its current state assuming the current tests pass anyway

https://github.com/aws/aws-lambda-dotnet/actions/runs/16602456157 running tests

rebased your changes on top of dev (which has a fix in the unit tests)

https://github.com/aws/aws-lambda-dotnet/actions/runs/16603533641 rerunning the tests

rerunning the tests - they are a little flaky and failing due to some unrelated issues. will try and get this merged in today