[APPSEC-55378] Rework Processor::Context logging and telemetry

[Strech]

What does this PR do?

This PR centralizes debug handling of the WAF execution into a single place Processor::Context

Motivation:

During upgrades we would like to know when we've made a mistake and be alerted about it upfront. We double-checked existing result codes of the WAF execution and removed outdated. At the same time if we use Telemetry error reporting to deliver unhandled errors such as:

• DDWAF_ERR_INTERNAL (ruby: :err_internal)
• DDWAF_ERR_INVALID_OBJECT (ruby: :err_invalid_object)
• DDWAF_ERR_INVALID_ARGUMENT (ruby: :err_invalid_argument)

See full list

Change log entry

Not needed.

Additional Notes:

This PR could be released without libddwaf-rb upgrade

How to test the change?

CI is enough.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.85%. Comparing base (d77045d) to head (dc1b88f).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4035      +/-   ##
==========================================
- Coverage   97.86%   97.85%   -0.01%     
==========================================
  Files        1321     1321              
  Lines       79343    79318      -25     
  Branches     3936     3904      -32     
==========================================
- Hits        77647    77616      -31     
- Misses       1696     1702       +6     

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[y9v]

I think we actually don't need this line, and this whole reject! could be changed to:

input.compact!.reject(&:empty?)

[y9v]

the only thing I am not sure is whether we can expect that every non-nil value responds to empty??

[y9v]

and it's also fine to leave this block like it is, to reduce amount of changes in this PR

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-10-28 18:26:02

Comparing candidate commit dc1b88f in PR branch appsec-55378-restructure-context-logging-and-telemetry with baseline commit d77045d in branch master.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 23 metrics, 2 unstable metrics.

scenario:library - Gem loading

• 🟥 throughput [-0.153op/s; -0.147op/s] or [-5.496%; -5.299%]

[Strech]

After discussion with @TonyCTHsu we agreed to change it into the following:

message = "libddwaf:1.14.0 execution error: #{result.status.inspect}"

we will drop result.inspect to balance cardinality and also it doesn't bring much value.