Fastify RASP support

[simon-id]

What does this PR do?

Add RASP support for Fastify.

This require creating a new system called "block delegation". Instead of blocking responses synchronously in the middle of a request/response cycle with block(). We register a "block delegation" with registerBlockDelegation() that will be picked up when the user/framework call response ending methods (res.writeHead(), res.end(), res.write()), and will then call the normal block() to send our blocking response in lieu of the user's response. A good ol' switcharoo.
This is to allow frameworks to follow their full request life-cycles, instead of us abruptly breaking continuity. For example it allows Fastify to call the onError, onSend and onResponse hooks correctly, which in turns allow more control on the cleanup of the request by the users.

ST PR: DataDog/system-tests#4963

[github-actions]

Overall package size

Self size: 11.92 MB
Deduped: 111.53 MB
No deduping: 111.87 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | @datadog/libdatadog | 0.7.0 | 35.02 MB | 35.02 MB | | @datadog/native-appsec | 10.1.0 | 20.37 MB | 20.37 MB | | @datadog/native-iast-taint-tracking | 4.0.0 | 11.72 MB | 11.73 MB | | @datadog/pprof | 5.9.0 | 9.77 MB | 10.1 MB | | @opentelemetry/core | 1.30.1 | 908.66 kB | 7.16 MB | | protobufjs | 7.5.4 | 2.95 MB | 5.6 MB | | @datadog/wasm-js-rewriter | 4.0.1 | 2.85 MB | 3.58 MB | | @datadog/native-metrics | 3.1.1 | 1.02 MB | 1.43 MB | | @opentelemetry/api | 1.8.0 | 1.21 MB | 1.21 MB | | jsonpath-plus | 10.3.0 | 617.18 kB | 1.08 MB | | import-in-the-middle | 1.14.2 | 122.36 kB | 850.93 kB | | lru-cache | 10.4.3 | 804.3 kB | 804.3 kB | | opentracing | 0.14.7 | 194.81 kB | 194.81 kB | | source-map | 0.7.6 | 185.63 kB | 185.63 kB | | pprof-format | 2.1.0 | 111.69 kB | 111.69 kB | | @datadog/sketches-js | 2.1.1 | 109.9 kB | 109.9 kB | | lodash.sortby | 4.7.0 | 75.76 kB | 75.76 kB | | ignore | 7.0.5 | 63.38 kB | 63.38 kB | | istanbul-lib-coverage | 3.2.2 | 34.37 kB | 34.37 kB | | rfdc | 1.4.1 | 27.15 kB | 27.15 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB | | @isaacs/ttlcache | 1.4.1 | 25.2 kB | 25.2 kB | | tlhunter-sorted-set | 0.1.0 | 24.94 kB | 24.94 kB | | shell-quote | 1.8.3 | 23.74 kB | 23.74 kB | | limiter | 1.1.5 | 23.17 kB | 23.17 kB | | retry | 0.13.1 | 18.85 kB | 18.85 kB | | semifies | 1.0.0 | 15.84 kB | 15.84 kB | | jest-docblock | 29.7.0 | 8.99 kB | 12.76 kB | | crypto-randomuuid | 1.0.0 | 11.18 kB | 11.18 kB | | ttl-set | 1.0.0 | 4.61 kB | 9.69 kB | | mutexify | 1.4.0 | 5.71 kB | 8.74 kB | | path-to-regexp | 0.1.12 | 6.6 kB | 6.6 kB | | koalas | 1.0.2 | 6.47 kB | 6.47 kB | | module-details-from-path | 1.0.4 | 3.96 kB | 3.96 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.80%. Comparing base (9469da8) to head (05f498e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6081      +/-   ##
==========================================
+ Coverage   83.76%   83.80%   +0.03%     
==========================================
  Files         477      477              
  Lines       20060    20078      +18     
==========================================
+ Hits        16804    16827      +23     
+ Misses       3256     3251       -5     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-08-28 04:06:26

Comparing candidate commit 05f498e in PR branch simon-id/fastify_rasp with baseline commit 9469da8 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1267 metrics, 56 unstable metrics.

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 05f498e | Docs | Was this helpful? Give us feedback!}

[uurien]

This TODO is not precise. We are calling to the method when the operation is not blocked. The bug is that if the operation is blocked but the request is not (for example: try catched blocked operation), we are not updating the metric neither with true nor false