fix: long variables pattern matching

[ablaszkiewicz]

We've encountered a problem where if variable value is too long, we are spending too much time inside the regex pattern matching.

This PR makes it so that if some value is longer than 5k characters, we replace it with a new $$_posthog_value_too_long_$$. I will soon make a change on the frontend to support this and display an appropriate message.

[github-actions]

posthog-python Compliance Report

Date: 2026-02-09 15:45:32 UTC
Duration: 159365ms

✅ All Tests Passed!

29/29 tests passed

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Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	517ms
Format Validation.Event Has Uuid	✅	1506ms
Format Validation.Event Has Lib Properties	✅	1507ms
Format Validation.Distinct Id Is String	✅	1506ms
Format Validation.Token Is Present	✅	1507ms
Format Validation.Custom Properties Preserved	✅	1507ms
Format Validation.Event Has Timestamp	✅	1507ms
Retry Behavior.Retries On 503	✅	9513ms
Retry Behavior.Does Not Retry On 400	✅	3509ms
Retry Behavior.Does Not Retry On 401	✅	3508ms
Retry Behavior.Respects Retry After Header	✅	9514ms
Retry Behavior.Implements Backoff	✅	23517ms
Retry Behavior.Retries On 500	✅	7517ms
Retry Behavior.Retries On 502	✅	7512ms
Retry Behavior.Retries On 504	✅	7507ms
Retry Behavior.Max Retries Respected	✅	23533ms
Deduplication.Generates Unique Uuids	✅	1497ms
Deduplication.Preserves Uuid On Retry	✅	7510ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14524ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7504ms
Deduplication.No Duplicate Events In Batch	✅	1508ms
Deduplication.Different Events Have Different Uuids	✅	1506ms
Compression.Sends Gzip When Enabled	✅	1508ms
Batch Format.Uses Proper Batch Structure	✅	1506ms
Batch Format.Flush With No Events Sends Nothing	✅	1005ms
Batch Format.Multiple Events Batched Together	✅	1505ms
Error Handling.Does Not Retry On 403	✅	3509ms
Error Handling.Does Not Retry On 413	✅	3507ms
Error Handling.Retries On 408	✅	7512ms