refactor: add generic type parameters for improved type flexibility

[tharropoulos]

TLDR

Added generic type parameters to API key, override, and document schemas for better type flexibility.

Change Summary

Code Changes:

1. In src/typesense/types/key.py:

   • Added _ActionT type variable with bounds for API key action type constraints
   • Made ApiKeyCreateSchema, ApiKeyCreateResponseSchema, ApiKeySchema, and ApiKeyRetrieveSchema generic with _ActionT parameter
   • Added backward compatibility aliases (ApiKeyCreateSchemaCompat, ApiKeySchemaCompat, etc.)
   • Replaced hardcoded _Actions union type with generic _ActionT parameter in actions field

2. In src/typesense/types/override.py:

   • Added _OverrideRuleT type variable for override rule type constraints
   • Made OverrideCreateSchema and OverrideSchema generic with _OverrideRuleT parameter
   • Added compatibility type aliases (OverrideCreateSchemaCompat, OverrideSchemaCompat)
   • Replaced hardcoded union type with generic parameter in rule field

3. In src/typesense/types/document.py:

   • Added _DocumentImportParamsT, _ImportResponseT, and _StringOrListT type variables
   • Added DocumentImportParametersGeneric type variable for document import parameters
   • Defined bounded type variables to improve type safety and flexibility

4. In src/typesense/__init__.py:

   • Bumped version from 1.2.0 to 1.2.1

Context

#90

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