ingest: encode PostHog project path segment

[sdivyanshu90]

Why

PostHogPullRequest.project_id accepts any nonblank string, but pull_posthog_traces inserted it directly into /api/projects/{project_id}/query/. Reserved and Unicode characters could therefore change the authorized request target instead of remaining one project path segment.

Closes #997.

What

• Percent-encode the PostHog project ID with an empty safe-character set before endpoint composition, including complete . and .. segments.
• Preserve the original project ID for source identity.
• Add a dedicated posthog_pull_test.py injected-client regression covering path, query, fragment, percent, space, and Unicode characters.

Validation

• Before the fix, test_project_id_is_encoded_as_one_url_path_segment failed with the raw project ID in the captured URL.
• uv run --no-sync pytest -q exp/simulation/ingest/posthog_pull_test.py exp/simulation/ingest/posthog_canonical_test.py: 21 passed in 1.21s
• uv run --no-sync ruff check .: passed
• uv run --no-sync ruff format --check .: 859 files already formatted
• uv run --no-sync ty check: passed

Non-goals

This change does not alter PostHog host validation, credentials, HogQL construction, response handling, or source identity.

[sdivyanshu90]

Hi @SilenNaihin, could you please review this when you have a chance? It keeps PostHog project IDs within one encoded path segment and adds a focused transport regression. Thanks!

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the previously reported dot-segment request-target issue is fully fixed.

Summary

The PR safely confines arbitrary PostHog project IDs to one URL path segment while retaining the original identifier for source identity.

• Percent-encodes reserved, whitespace, percent, and Unicode characters before endpoint composition.
• Explicitly encodes complete . and .. segments to prevent HTTP path normalization.
• Adds focused regression coverage for reserved characters, Unicode, and both dot-segment cases.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    A[Original project ID] --> B[Percent-encode path segment]
    B --> C{Complete dot segment?}
    C -- Yes --> D[Encode periods as %2E]
    C -- No --> E[Use encoded segment]
    D --> F[Compose PostHog query endpoint]
    E --> F
    A --> G[Preserve original source identity]

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[sdivyanshu90]

@kfallah Could you please review this PR whenever you have some time? Thanks

[sdivyanshu90]

Hi @SilenNaihin @kfallah, could you please review this PR whenever you have some time. Thanks!