Netlify CLI server does not properly handle content-type to determine base64 body

[kiliman]

Currently when the server checks shouldBase64Encode() it's passing in the content-type header. This function makes a series of checks and compares to an exclusion list. However, if the content-type header is something like application/json; charset=utf-8 segment, this causes the exclusion list to not match and always returns true.

Oddly, even though isBase64Encoded is true, it doesn't seem to encode it to base64 data. So when processing the event and checking isBase64Encoded and converting from base64, it results in invalid binary data.

This was found while debugging a Remix/Stripe integration that only failed on the Netlify adapter. See this Discord thread for more details.

https://discord.com/channels/770287896669978684/940734316298797076/940739970874867793