feat: adding gemini and XAI

[epsjunior]

Brief Overview

• Added support for Gemini and XAI LLM providers
• Expanded .env.example to include new API keys
• Updated internal AI provider types and configuration

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🔹 Problem Solved

• Missing support for Gemini and XAI LLMs in provider configuration

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🔹 Changes Made

Provider Support

• Added "geminiai" and "xai" to AiProviders union type
• Included "GEMINI_API_KEY" and "XAI_API_KEY" in AiProvidersEnvVars
• Expanded AI_PROVIDERS_CONFIG with configuration for Gemini and XAI

Environment Variables

• Extended .env.example with placeholders for:
  • GEMINI_API_KEY
  • XAI_API_KEY
• Added usage hints to guide developers on configuration requirements

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🔹 Important Decisions

• Kept backward compatibility by preserving current provider structures

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🔹 Previously Aligned Architecture Changes

• Built upon existing AI_PROVIDERS_CONFIG structure
• No refactor required; changes focused on data extension only

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (ae8b5fe) to head (0da43b7).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #216   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           29        29           
  Lines         1505      1534   +29     
  Branches       373       381    +8     
=========================================
+ Hits          1505      1534   +29     

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