fix: complete emulator REST APIGatewayProxyRequest and null-safe AspNetCoreServer marshalling

[msmourao]

Issue #, if available:
Fixes #2566

Description of changes:
When the Lambda Test Tool v2 API Gateway emulator translates an HTTP request into a REST APIGatewayProxyRequest, it omitted RequestContext and could leave Path / HttpMethod null. Amazon.Lambda.AspNetCoreServer then threw NullReferenceException while marshalling those incomplete events into ASP.NET Core features.

This PR:

1. Amazon.Lambda.TestTool — populate a minimal RequestContext (and default Path/HttpMethod) for emulator-built REST proxy events, closer to real API Gateway / test-invoke payloads. HTTP API v2 translation already set RequestContext.
2. Amazon.Lambda.AspNetCoreServer — null-safe marshalling for Path, HttpMethod, path parameters, and header values so incomplete events do not NRE.

Includes an AutoVer change file (Patch) for both projects.

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

[normj]

Thanks for the fix!

[msmourao]

Thanks for the fix!

Hi, @normj! Glad to help! This is my secondone after a fix about multiple message hendlers in a same lambda, and there is a feature request that I o opened about allowing other kind of requests through API Gateway to a better mimic of a real environment.

These are working on my fork and are a part of a big change on how Aspire works I implemented to allow you to write your applications in a cloud-agnostic way and too many other features to list in here.

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