litellm Add User ID validation to ensure it is not an email or phone number

Title

Add validation to exclude invalid user_id (e.g. email or phone number) from Anthropic metadata

Relevant issues

Fixes #10106

Type

🐛 Bug Fix

Changes

This PR introduces a validation check for the user_id field in the _litellm_metadata dictionary to ensure it does not contain personally identifiable information (PII) such as emails or phone numbers.

Rationale

Anthropic requires that the user_id in metadata must be a UUID, hash value, or other opaque, non-identifying identifier. It must not contain any personally identifiable information such as names, email addresses, or phone numbers. Including such data can lead to the API rejecting the request with a 400 Bad Request error. View

This update ensures that if an invalid user_id is provided (e.g. an email), it will simply be excluded from the metadata, preventing avoidable request failures.