fix(appsec): should not run sampler if the content cannot be parsed

[eliottness]

What does this PR do?

Fixes an issue that would trigger body analysis even if we were not capable of parsing said-body.

Motivation

Parse body more ofter because sampling would not trigger on wrong requests

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running ./scripts/lint.sh locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

Unsure? Have a question? Request a review!

[eliottness]

/merge

[dd-devflow-routing-codex]

View all feedbacks in Devflow UI.

2025-11-07 14:10:20 UTC ℹ️ Start processing command /merge

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2025-11-07 14:10:29 UTC ℹ️ MergeQueue: waiting for PR to be ready

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2025-11-07 18:11:11 UTC ⚠️ MergeQueue: This merge request was unqueued

devflow unqueued this merge request: It did not become mergeable within the expected time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-11-10 15:24:47

Comparing candidate commit ac83cb0 in PR branch eliottness/api10-better-sampling with baseline commit 1557bbd in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 15 metrics, 0 unstable metrics.