📝 Add docstrings to feat/regexp_model_map

Docstrings generation was requested by @ytti.

* #3362 (comment)

The following files were modified:

* `lib/oxidized/source/source.rb`

lib/oxidized/source/source.rb

@@ -3,11 +3,30 @@ module Source
     class Source
       class NoConfig < OxidizedError; end
 
+      # @see Oxidized.config
       def initialize
         @model_map = Oxidized.config.model_map || {}
         @group_map = Oxidized.config.group_map || {}
       end
 
+      ##
+      # Maps an original value to a new value based on a hash of mapping rules.
+      #
+      # This method iterates through a mapping hash and attempts to match the original value
+      # against each key using either regular expression matching or direct equality.
+      #
+      # @param [Hash] map_hash A hash containing mapping rules where keys can be Regexp or other objects
+      # @param [Object] original_value The value to be mapped
+      # @return [Object] The mapped value if a match is found, otherwise the original value
+      #
+      # @example Mapping with regular expression
+      #   map_value({/^web/ => 'web_server'}, 'web01') # Returns 'web_server'
+      #
+      # @example Mapping with direct equality
+      #   map_value({'old_name' => 'new_name'}, 'old_name') # Returns 'new_name'
+      #
+      # @example No match scenario
+      #   map_value({/^db/ => 'database'}, 'web01') # Returns 'web01'
       def map_value(map_hash, original_value)
         map_hash.each do |key, new_value|
           mthd = key.instance_of?(Regexp) ? :match : :eql?
@@ -16,14 +35,33 @@ def map_value(map_hash, original_value)
         original_value
       end
 
+      # @return [String] The mapped model name, or the original model if no mapping exists.
       def map_model(model)
         map_value(@model_map, model)
       end
 
+      # @return [String] The mapped group name or the original group if no mapping exists.
       def map_group(group)
         map_value(@group_map, group)
       end
 
+      ##
+      # Interpolates a string representation of a variable to its corresponding Ruby value.
+      #
+      # This method converts string representations of boolean and nil values to their
+      # respective Ruby types. It handles the following conversions:
+      # - "nil" becomes nil
+      # - "false" becomes false
+      # - "true" becomes true
+      # - Any other string value is returned as-is
+      #
+      # @param [String] var The string to be interpolated
+      # @return [Object] The interpolated value (nil, false, true, or the original string)
+      # @example
+      #   node_var_interpolate("nil")   # => nil
+      #   node_var_interpolate("false") # => false
+      #   node_var_interpolate("true")  # => true
+      #   node_var_interpolate("hello") # => "hello"
       def node_var_interpolate(var)
         case var
         when "nil"   then nil