Add Faraday instrumentation for AppSec

[y9v]

What does this PR do?
This PR adds Faraday instrumentation to AppSec for Server-Side Request Forgery detection.

Motivation:
We want to detect SSRF attacks on applications using Faraday as the http client. Support for more http clients (excon and rest-client) will be added in subsequent PRs.

Change log entry
Yes. AppSec: Add detection of Server-Side Request Forgery attacks for Faraday http client.

Additional Notes:
Patcher is heavily inspired by our Tracing Faraday patcher.

How to test the change?
CI and manual testing with app-generator (rails-ssrf variant)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-18 09:54:45

Comparing candidate commit 0158995 in PR branch appsec-add-faraday-instrumentation with baseline commit bcf28ce in branch master.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 30 metrics, 2 unstable metrics.

scenario:tracing - Propagation - Trace Context

• 🟥 throughput [-3022.972op/s; -2927.621op/s] or [-8.152%; -7.895%]

[datadog-datadog-prod-us1]

Datadog Report

Branch report: appsec-add-faraday-instrumentation
Commit report: 0158995
Test service: dd-trace-rb

✅ 0 Failed, 20398 Passed, 1373 Skipped, 3m 12.28s Total Time

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.13665% with 3 lines in your changes missing coverage. Please review.

Project coverage is 97.71%. Comparing base (bcf28ce) to head (0158995).

Files with missing lines	Patch %	Lines
...og/appsec/contrib/integration/faraday_ssrf_spec.rb	95.65%	2 Missing ⚠️
lib/datadog/appsec/contrib/faraday/integration.rb	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4391      +/-   ##
==========================================
- Coverage   97.71%   97.71%   -0.01%     
==========================================
  Files        1354     1361       +7     
  Lines       83085    83246     +161     
  Branches     4219     4226       +7     
==========================================
+ Hits        81188    81341     +153     
- Misses       1897     1905       +8     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Strech]

Awesome to see that we have a solid ground to develop integrations. I left a few comments over naming and testing because I think we could do better and simplify even more

[Strech]

Awesome 👏🏼

I have a few non-blocking suggestions, but for tests it's an important.