Describe the solution you'd like
Create a go openai plugin per conversation with @apascal07.

Additional context
Genkit value: getting structured data in and out. Core features of this plugin should be that we convert to/from genkit's structured format to OpenAI's format. Ensure that we are mapping this structure to/from the genkit and openai.

Requirements:

• Genkit sample with the OpenAI plugin
• OpenAI client (either custom or the official)
• Support streaming for the plugin
• Chat completions endpoint (we can start with text, move to other if necessary)