[Ruby] Fix "build_from_hash" function for Ruby enums (#6812)

* Modify build_from_hash to compare value against enum's value rather than const name

* Updated Petstore sample

Author: Renaud Amar

modules/swagger-codegen/src/main/resources/ruby/partial_model_enum_class.mustache

@@ -6,8 +6,8 @@
     # @param [String] The enum value in the form of the string
     # @return [String] The enum value
     def build_from_hash(value)
-      consantValues = {{classname}}.constants.select{|c| c.to_s == value}
-      raise "Invalid ENUM value #{value} for class #{{{classname}}}" if consantValues.empty?
+      constantValues = {{classname}}.constants.select{|c| {{classname}}::const_get(c) == value}
+      raise "Invalid ENUM value #{value} for class #{{{classname}}}" if constantValues.empty?
       value
     end
   end

samples/client/petstore/ruby/lib/petstore/models/enum_class.rb

@@ -23,8 +23,8 @@ class EnumClass
     # @param [String] The enum value in the form of the string
     # @return [String] The enum value
     def build_from_hash(value)
-      consantValues = EnumClass.constants.select{|c| c.to_s == value}
-      raise "Invalid ENUM value #{value} for class #EnumClass" if consantValues.empty?
+      constantValues = EnumClass.constants.select{|c| EnumClass::const_get(c) == value}
+      raise "Invalid ENUM value #{value} for class #EnumClass" if constantValues.empty?
       value
     end
   end

samples/client/petstore/ruby/lib/petstore/models/outer_enum.rb

@@ -23,8 +23,8 @@ class OuterEnum
     # @param [String] The enum value in the form of the string
     # @return [String] The enum value
     def build_from_hash(value)
-      consantValues = OuterEnum.constants.select{|c| c.to_s == value}
-      raise "Invalid ENUM value #{value} for class #OuterEnum" if consantValues.empty?
+      constantValues = OuterEnum.constants.select{|c| OuterEnum::const_get(c) == value}
+      raise "Invalid ENUM value #{value} for class #OuterEnum" if constantValues.empty?
       value
     end
   end