Add Azure OpenAI embedding provider to fix registry KeyError

[divya-garak]

Summary

This PR adds a missing Azure OpenAI embedding provider to fix the KeyError: 'azure' does not exist in the registry error reported in issue #1268.

Changes Made

• New Azure OpenAI Embedding Provider: Implemented AzureOpenAIEmbeddingModel class in nemoguardrails/embeddings/providers/azure.py

  • Full Azure OpenAI API integration using the openai package
  • Supports both known embedding models and custom Azure deployment names
  • Automatic embedding size detection for custom deployments
  • Proper error handling for missing OpenAI dependency

• Provider Registration: Added azure provider to the embedding provider registry in __init__.py

• Comprehensive Test Suite: Created tests/test_azure_embedding_provider.py with 6 test cases:

  • Provider registration verification
  • Model initialization with different parameters
  • Custom deployment name handling
  • Encoding functionality testing
  • Error handling for missing dependencies
  • Integration with provider registry

Technical Details

The Azure provider uses the same embedding models as OpenAI (text-embedding-ada-002, text-embedding-3-small, text-embedding-3-large) but connects to Azure OpenAI endpoints. For custom deployment names, it performs an initial encoding call to determine the embedding size automatically.

Testing

All 6 test cases pass, covering:

• ✅ Provider registration and retrieval
• ✅ Initialization with various parameters
• ✅ Custom deployment support
• ✅ Encoding functionality
• ✅ Error handling
• ✅ Registry integration

Fixes

Closes #1268

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update