Support OpenAI compatible providers through a base URL

docs/guides/getting-started.md

@@ -33,6 +33,12 @@ RubyLLM.configure do |config|
 end
 ```
 
+You can optionally provide the base URL for the OpenAI API, through which you can point to OpenAI API compatible engines like [Ollama](https://github.com/ollama/ollama), [KoboldCPP](https://github.com/LostRuins/koboldcpp), [TabbyAPI](https://github.com/theroyallab/tabbyAPI), etc:
+
+```ruby
+  config.openai_base_url = "http://localhost:11434/v1"
+```
+
 ## Your First Chat
 
 Let's start with a simple chat interaction:
@@ -161,4 +167,4 @@ Now that you've got the basics down, you're ready to explore more advanced featu
 
 - [Chatting with AI]({% link guides/chat.md %}) - Learn more about chat capabilities
 - [Using Tools]({% link guides/tools.md %}) - Let AI use your Ruby code
-- [Rails Integration]({% link guides/rails.md %}) - Persist chats in your Rails apps
+- [Rails Integration]({% link guides/rails.md %}) - Persist chats in your Rails apps

lib/ruby_llm/configuration.rb

@@ -11,6 +11,7 @@ module RubyLLM
   #   end
   class Configuration
     attr_accessor :openai_api_key,
+                  :openai_base_url,
                   :anthropic_api_key,
                   :gemini_api_key,
                   :deepseek_api_key,

lib/ruby_llm/providers/openai.rb

@@ -29,7 +29,7 @@ def self.extended(base)
       module_function
 
       def api_base
-        'https://api.openai.com/v1'
+        RubyLLM.config.openai_base_url || 'https://api.openai.com/v1'
       end
 
       def headers