HTTP header names should be case insensitive

[AndrewSav]

Describe the bug

where we configure headers like this:

endpoints:
  - headers:
      user-agent: Mozilla/5.0

due to how gatus is coded and maps in golang work, it's a toss up will we get mozilla or gatus header effectively applied to request, so results are random. Can we fix this so that the header names are truly case insensitive as they should be?

What do you see?

endpoints fail intermittently due to wrong header sent

What do you expect to see?

the header is sent as specified in configuration without another header of the same name being sent by gatus itself

List the steps that must be taken to reproduce this issue

1. use the headers config similar to above
2. observe on the server polled that headers received are mixed

Version

5.34.0

Additional information

No response

[TwiN]

I agree with you, this is clearly a bug and an oversight on my part.

As per RFC 7230, header names should be case-insensitive.

[AndrewSav]

If someone else comes across this, the work around is to use User-Agent and Content-Type capitalisation in the headers section of your configuration.

[AnuragEkkati]

Can I work on this issue ?

[AnuragEkkati]

@TwiN, can you please review the fix PR #1506