Credential headers are case sensitive

[xcodian]

The headers, when set using the username and password keys work, but do not when they are cased as Username and Password.

This is the line probably responsible for this check, it should probably be doing a case insensitive comparison.
https://github.com/taskcollect/email-getter/blob/e6da0e886df116d8e3f9aa272fb40cbc3a77f6b6/src/Controllers/EmailController.cs#L30

Why is this a problem?
It's not really a big one, it's just that Go's http client always capitalizes the first letter, and other HTTP clients must explicitly be told that the header should maintain the lowercase.

Thanks.

PS. This entire credential passing should either happen through basic auth or in the request body. This is fine for the moment though.