Add support for external-id properties on lexemes

[robertsilen]

With the help of Cursor AI and Claude, I addeed support for adding external-id claims to lexemes. I have been using this version of LexData now for creating lexemes and it works, see e.g. P12682 in L1463924. I have not tested other cases, not sure what they could be. As the solution is generated by GenAI, I don't have a deep understanding if the solution is sound - could you @Nudin can evaluate if this is suitable to merge with the project? The following is generated by GenAI and review by me:

Problem
LexData currently doesn't support adding external-id claims to lexemes. When attempting to add external-id properties (like P12682) to lexemes, the API returns errors like:

• "invalid-snak" when using wbcreateclaim with plain string values
• "Type 'external-id' is unsupported" when using wbeditentity

Root Cause
The Wikidata API expects external-id values to be sent as JSON-encoded strings (e.g., '"value"') rather than plain strings ('value'). Additionally, the pure_value property in the Claim class didn't handle the external-id data type.

Solution

1. Added external-id support in utils.py: Extended buildDataValue() to handle external-id data type correctly
2. Fixed pure_value in claim.py: Added support for extracting values from external-id claims
3. Updated entity.py: Modified setClaim to JSON-encode external-id values before sending to API
4. Enhanced setEntityClaim: Added detection and proper handling of external-id properties

Changes Made

• LexData/utils.py: Added "external-id" to supported data types
• LexData/claim.py: Added external-id case in pure_value property
• LexData/entity.py: Updated claim creation logic to handle external-id properly

Testing
Verified that external-id claims can now be successfully added to lexemes:

claim = LexData.Claim(propertyId="P12682", value="some_external_id")
lexeme.addClaims([claim])

Questions for Review

1. Is this the right approach? I used wbcreateclaim for lexemes (which works) rather than wbeditentity (which fails with external-id). Should we investigate why wbeditentity doesn't support external-id on lexemes?
2. API consistency: The Wikidata API seems to have different behavior for external-id properties on lexemes vs items. Is this expected, or should we file a bug report with Wikidata?
3. Error handling: Should we add more specific error handling for external-id properties, or is the current approach sufficient?