CDK: Allow to whitelist headers

[Negan1911]

Hello, first of all thanks for this great library, and thanks for porting it to CDK.

Currently, I'm working on a Cloudfront app that has the domain as *.mypage.com

Where * is a brand selected by our customers, identifying it has become difficult for a couple of reasons:

• I don't know how to access the original event sent to the lambda (I also don't know how I can implement this one) so I went to the 2nd option which is reading the Host header.
• When reading the Host header on SSR, it works quite well, except when the request is to _next/data, in that case, the Host header is from CloudFront because it's not being forwarded, this PR adds the ability to forward headers.

I've tried to keep it up with what was needed, it was being tested by my end and I added a unit test, please let me know if I'm missing something, also, if you have some clues on how to read the original event on nextjs getServerSideProps. I would love to implement that on another PR.

Again, thank you!

[slsnextbot]

Handler Size Report

No changes to handler sizes.

Base Handler Sizes (kB) (commit 9facd15)

{
    "Lambda": {
        "Default Lambda": {
            "Standard": 1524,
            "Minified": 668
        },
        "Image Lambda": {
            "Standard": 1488,
            "Minified": 800
        }
    },
    "Lambda@Edge": {
        "Default Lambda": {
            "Standard": 1534,
            "Minified": 673
        },
        "Default Lambda V2": {
            "Standard": 1526,
            "Minified": 670
        },
        "API Lambda": {
            "Standard": 634,
            "Minified": 318
        },
        "Image Lambda": {
            "Standard": 1496,
            "Minified": 805
        },
        "Regeneration Lambda": {
            "Standard": 1187,
            "Minified": 546
        },
        "Regeneration Lambda V2": {
            "Standard": 1253,
            "Minified": 573
        }
    }
}

New Handler Sizes (kB) (commit 803efb7)

{
    "Lambda": {
        "Default Lambda": {
            "Standard": 1524,
            "Minified": 668
        },
        "Image Lambda": {
            "Standard": 1488,
            "Minified": 800
        }
    },
    "Lambda@Edge": {
        "Default Lambda": {
            "Standard": 1534,
            "Minified": 673
        },
        "Default Lambda V2": {
            "Standard": 1526,
            "Minified": 670
        },
        "API Lambda": {
            "Standard": 634,
            "Minified": 318
        },
        "Image Lambda": {
            "Standard": 1496,
            "Minified": 805
        },
        "Regeneration Lambda": {
            "Standard": 1187,
            "Minified": 546
        },
        "Regeneration Lambda V2": {
            "Standard": 1253,
            "Minified": 573
        }
    }
}

[codecov]

Codecov Report

Merging #2325 (803efb7) into master (9facd15) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2325      +/-   ##
==========================================
+ Coverage   83.63%   83.65%   +0.01%     
==========================================
  Files         104      104              
  Lines        3716     3719       +3     
  Branches     1194     1197       +3     
==========================================
+ Hits         3108     3111       +3     
  Misses        596      596              
  Partials       12       12              

Impacted Files	Coverage Δ
...rless-components/nextjs-cdk-construct/src/index.ts	93.57% <100.00%> (+0.18%)	⬆️

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[dphang]

Thanks, it LGTM