fix(api): fix incorrect path handling in Langfuse integration

[chenguowei]

Solve the problem of langfuse configuration error resolves #22757

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Summary

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Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[crazywoola]

Please fix the tests.

[Nov1c444]

Maybe It's the better way to fix the issue.
change the validate_endpoint_url method in config_entity.py

[chenguowei]

The validate_url function itself only verifies whether the url is correct and should not change the original url. This is the definition of a validation function.

[QuantumGhost]

@chenguowei I agree with your principle that validate_url should focus solely on URL validation without modifying the input. However, I'm concerned about the potential impact of this change on the existing codebase.

The validate_url function is used across multiple locations in the codebase, and changing its behavior from returning a normalized URL to returning the original URL could introduce breaking changes in other components that depend on the current normalization behavior.

I suggest a more conservative approach:

1. Introduce validate_url_with_path for cases where path preservation is needed (like Langfuse configuration)
2. Mark validate_url as deprecated
3. Gradually migrate existing usages to the appropriate function based on their requirements.

[Hammad663]

Not interested in your artifactsi

[chenguowei]

by modifying case by case in this way, I understand that other subsequent modifications may also need to be made successively

[QuantumGhost]

@chenguowei Yes, I understand your concern about potential cascading changes. However, it appears that other integrations are working fine with the current approach. Let's keep it as-is for now and monitor if similar issues arise elsewhere.