Stricter error reporting for malformed headers

[NHDaly]

Please specify the following versions when submitting a bug report:

• Julia 1.7.3
• HTTP.jl 1.3.1
• MbedTLS.jl 1.1.3

We had an issue where our requests weren't working as expected. We eventually debugged the issue down to a bug in how we were specifying headers - we were accidentally passing headers = ["key", "value"] instead of headers = ["key" => "value"].

This means that we were accidentally passing two separate header strings, which were being interpreted as e.g. "key"[1] => "key"[2], or 'k'=>'e' and 'v'=>'a'. You can see this in action here:

julia> HTTP.request("GET", "http://example.com", headers=["hello","world"], verbose=3);
┌ LogLevel(-1001): GET / HTTP/1.1
└ @ HTTP.StreamRequest ~/.julia/packages/HTTP/cwiB4/src/clientlayers/StreamRequest.jl:24
┌ LogLevel(-1002): client startwrite
└ @ HTTP.StreamRequest ~/.julia/packages/HTTP/cwiB4/src/clientlayers/StreamRequest.jl:25
┌ LogLevel(-1003): 👁  Start write:🔁    4s example.com:80:61559 RawFD(36)
└ @ HTTP.ConnectionPool ~/.julia/packages/HTTP/cwiB4/src/ConnectionPool.jl:229
┌ LogLevel(-1002): HTTP.Messages.Request:
│ """
│ GET / HTTP/1.1
│ h: e
│ w: o
│ Host: example.com
│ Accept: */*
│ User-Agent: HTTP.jl/1.7.3-pre.8
│ Content-Length: 0
│ Accept-Encoding: gzip
│ 
│ """
└ @ HTTP.StreamRequest ~/.julia/packages/HTTP/cwiB4/src/clientlayers/StreamRequ

Can we have this situation print an error instead? If you pass a header value that has more than 2 elements, can that be an error? And if you pass a header value that is of type String, can that be an error? E.g. can all of these situations be errors:

HTTP.request("GET", "http://example.com", headers=["hello"], verbose=3);
HTTP.request("GET", "http://example.com", headers=[(1,2,3,4,5), (2,3,4,5,6)], verbose=3);
HTTP.request("GET", "http://example.com", headers=[1, 2], verbose=3);   # <-- this is already an error (since `1[2]` fails)
HTTP.request("GET", "http://example.com", headers=["hello", "world"], verbose=3);

Thank you! 😊

[quinnj]

Thanks for the report @NHDaly! PR up: #919

[NHDaly]

❤️ so fast. Thank you! 😊 ❤️