docs: add comprehensive documentation to ApiClient class

lib/kalshi/api_client.rb

@@ -2,18 +2,53 @@
 
 module Rubyists
   module Kalshi
-    # API Client Base Class
+    # Base class for API client wrappers that automatically configure URL prefixes
+    #
+    # This class provides a foundation for building API clients that need to
+    # communicate with different API namespaces. It automatically extracts the
+    # prefix from the module hierarchy and applies it to the underlying HTTP client.
+    #
+    # @example Using ApiClient with a Search namespace
+    #   # For Rubyists::Kalshi::Search::Client, the prefix will be "search"
+    #   class Search::Client < ApiClient
+    #     # API calls will automatically use /search/ prefix
+    #   end
+    #
+    # @example Overriding the automatic prefix
+    #   class CustomClient < ApiClient
+    #     self.prefix = 'custom_api'
+    #   end
     class ApiClient
       attr_reader :client
 
+      # Automatically extract the URL prefix from the module hierarchy
+      #
+      # The prefix is derived by taking the second-to-last component of the
+      # fully qualified class name and converting it to lowercase. For example:
+      #   - Rubyists::Kalshi::Search::Client => "search"
+      #   - Rubyists::Kalshi::Market::Client => "market"
+      #
+      # @return [String] the URL prefix for API calls
       def self.prefix
         @prefix ||= to_s.split('::')[-2].downcase
       end
 
+      # Set a custom URL prefix, overriding the automatic extraction
+      #
+      # @param value [String] the custom prefix to use for API calls
+      #
+      # @return [String] the prefix value
       def self.prefix=(value) # rubocop:disable Style/TrivialAccessors
         @prefix = value
       end
 
+      # Initialize the API client with the given HTTP client
+      #
+      # Automatically configures the client's prefix based on the class hierarchy
+      #
+      # @param client [Client] the Kalshi HTTP client instance
+      #
+      # @return [void]
       def initialize(client)
         @client = client
         client.prefix = self.class.prefix