fix: tool parameter mapping for chat completions

[agarcher]

When consumers supply tools that use a full OpenAI::Chat::ChatCompletionTool rather than providing only an OpenAI::BaseModel, the calls to OpenAI fail because the tools argument winds up invalid. The mapping in the library overwrites the tool in the array with nil because there are missing return values from the second and third options of the case statement.

my_function_definition = OpenAI::Models::FunctionDefinition.new(
  name: "my_tool_name",
  description: "My tool description",
  parameters: OpenAI::BaseModel.new({ ... })
)
my_tool_definition = OpenAI::Chat::ChatCompletionTool.new(
  type: :function,
  function: my_function_definition
)
openai_client.chat.completions.create(
  ...
  tools: [my_tool_definition]
)

[ms-jpq]

ohh, thank you so much for fixing this!