[Ruby][client] Handle enums (and other scalars) in oneOf and anyOf schemas (#17515)

* Handle enums in oneOf and anyOf schemas

* Update specs

samples/client/petstore/ruby/docs/Cow.md

@@ -0,0 +1,15 @@
+# Petstore::Cow
+
+## Properties
+
+| Name | Type | Description | Notes |
+| ---- | ---- | ----------- | ----- |
+
+## Example
+
+```ruby
+require 'petstore'
+
+instance = Petstore::Cow.new()
+```
+

samples/client/petstore/ruby/docs/MamalWithEnum.md

@@ -0,0 +1,47 @@
+# Petstore::MamalWithEnum
+
+## Class instance methods
+
+### `openapi_one_of`
+
+Returns the list of classes defined in oneOf.
+
+#### Example
+
+```ruby
+require 'petstore'
+
+Petstore::MamalWithEnum.openapi_one_of
+# =>
+# [
+#   :'Cow'
+# ]
+```
+
+### build
+
+Find the appropriate object from the `openapi_one_of` list and casts the data into it.
+
+#### Example
+
+```ruby
+require 'petstore'
+
+Petstore::MamalWithEnum.build(data)
+# => #<Cow:0x00007fdd4aab02a0>
+
+Petstore::MamalWithEnum.build(data_that_doesnt_match)
+# => nil
+```
+
+#### Parameters
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| **data** | **Mixed** | data to be matched against the list of oneOf items |
+
+#### Return type
+
+- `Cow`
+- `nil` (if no type matches)
+