add embedder tests

[evanmschultz]

Add Tests for Embedder Implementations

Changes

• Added test suite for OpenAI, Gemini, and VoyageAI embedder implementations
• Created test fixtures to generate mock embedding values
• Implemented tests for both single and batch embedding operations

Technical Details

• Added test files:
  • embedder_fixtures.py: Utility function for creating mock embedding values
  • test_openai.py: Tests for OpenAI embedder
  • test_gemini.py: Tests for Gemini embedder
  • test_voyage.py: Tests for VoyageAI embedder
• Each test file includes:
  • Mock responses for API clients
  • Tests for API parameter validation
  • Tests for proper response processing
  • Tests for both single and batch embedding methods

I have read the CLA Document and I hereby sign the CLA

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[!IMPORTANT] Add tests for OpenAI, Gemini, and VoyageAI embedders, including single and batch operations, with mock API interactions.

• Tests:
  • Added test_openai.py, test_gemini.py, test_voyage.py for OpenAI, Gemini, and VoyageAI embedders.
  • Each test file includes tests for single and batch embedding operations, API parameter validation, and response processing.
  • Utilizes mock responses and clients to simulate API interactions.
• Fixtures:
  • Added embedder_fixtures.py for creating mock embedding values.
  • Provides utility function create_embedding_values() for generating mock data.

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[evanmschultz]

Partially addresses issue #375