Feat: Perplexity support

[joaoGabriel55]

Issue

#20

Description

This PR consists on add Perplexity API support

• models: https://docs.perplexity.ai/guides/model-cards;
• pricing: https://docs.perplexity.ai/guides/pricing

[joaoGabriel55]

Please, let me know if there is something missing on this first implementation

Question: How can I run tests locally?

[adenta]

How do I test?
You should be able to set API keys locally and run rspec to test the application.

@joaoGabriel55 I started a pull request here. Do you want to either tweak what I have, or incorporate my changes into your branch?

[gquaresma-godaddy]

@adenta let me know if there is something to improve

[adenta]

@gquaresma-godaddy we need tests! Want to take a crack at it?

[gquaresma-godaddy]

Sure! I will work on it.

[crmne]

Looks very good. It looks like sonar has support for vision, so it would need to be added to the chat_content_spec vision test, and the chat_streaming_spec.

[crmne]

Two new features to consider in your provider implementation:

1. Model Aliases: Please add entries for your provider in aliases.json:

   "claude-3-5-sonnet": {
     "anthropic": "claude-3-5-sonnet-20241022",
     "your-provider": "your-provider-specific-id"
   }

2. Provider Selection: Users will be able to specify your provider:

   chat = RubyLLM.chat(model: 'claude-3-5-sonnet', provider: 'your-provider')

Docs: https://rubyllm.com/guides/models#using-model-aliases

[crmne]

Added configuration requirements handling in 75f99a1

Each provider now specifies what configuration is required via a simple configuration_requirements method (you will need to implement this in your main provider file) that returns an array of config keys as symbols. The Provider module uses this to:

1. Determine if a provider is properly configured
2. Throw an error if you're trying to use that provider without configuration
3. Include ready-to-paste configuration code in the error message
4. Skip unconfigured providers during model refresh while preserving their models

Example of the new error messages:

RubyLLM::ConfigurationError: anthropic provider is not configured. Add this to your initialization:

RubyLLM.configure do |config|
  config.anthropic_api_key = ENV['ANTHROPIC_API_KEY']
end

[crmne]

@joaoGabriel55 is this still on your radar? I'd love to merge Perplexity support soon. Whenever you're ready, could you resolve the conflicts and request a review?

[crmne]

Thank you for your work!

It looks generally good, I just need some changes and tests. Please pick the cheapest model to test with.