[EXPORTER] Log SSL Connection Information

[chusitoo]

Fixes #2250

Changes

Enable curl verbose output and add debug function callback to intercept the "interesting" logs.

This functionality is controlled by the compile-time flag/option WITH_CURL_LOGGING=ON but can also be enabled at runtime by setting OtlpHttpExporterOptions::console_debug = true.

By default, all the headers and other information are not available and protected by a compile-time flag since they could contain sensitive information.

An example of info logging related to TLS handshake, available by default:

[Info] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:593 SSL connection using TLSv1.3 / TLS_AES_128_GCM_SHA256 / X25519 / RSASSA-PSS

An example of debug logging, enabled via -DOTEL_CURL_DEBUG:

[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:613 Send header => POST /v1/traces HTTP/2
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:613 Send header => Host: localhost:4318
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:613 Send header => Accept: */*
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:613 Send header => Content-Type: application/x-protobuf
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:613 Send header => User-Agent: OTel-OTLP-Exporter-Cpp/1.17.0
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:613 Send header => Content-Length: 238
[Debug] File: /otel/exporters/otlp/src/otlp_http_client.cc:226 [OTLP HTTP Client] Session state: sending request
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:602 We are completely uploaded and fine
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:620 Recv header => HTTP/2 200
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:620 Recv header => content-type: application/x-protobuf
[Debug] File: /otel/ext/src/http/client/curl/http_operation_curl.cc:620 Recv header => content-length: 2

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.85%. Comparing base (497eaf4) to head (17b4c57).
Report is 156 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3113      +/-   ##
==========================================
+ Coverage   87.12%   87.85%   +0.73%     
==========================================
  Files         200      195       -5     
  Lines        6109     6138      +29     
==========================================
+ Hits         5322     5392      +70     
+ Misses        787      746      -41     

see 100 files with indirect coverage changes

[marcalff]

Great work, thanks for the feature.

Reusing console_debug for this is a good idea.

See some comments or questions, with approval to follow once resolved.

[lalitb]

LGTM. Thanks for the contribution.

[marcalff]

LGTM, thanks for the feature.