Ollama images

[ccreutzi]

• Refactor messageHistory to be agnostic of the image encoding.
• Add backend encoding of images to openAIChat, azureChat, and ollamaChat.
• Add image test points to the test files.

As for the image encoding, Azure expects messages like this:

{ 
    "messages": [ 
        { "role": "system", "content": "You are a helpful assistant." }, 
        { "role": "user", "content": [  
            { 
                "type": "text", 
                "text": "Describe this picture:" 
            },
            { 
                "type": "image_url",
                "image_url": {
                    "url": "<image URL>"
                }
            }
        ] } 
    ], 
    "max_tokens": 2000 
} 

where <image URL> can be a “normal” URL like "https://somewhere.tld/filepath.png" or an inline URL like "data:image/jpeg;base64,{base64_image}".

Multiple images can be in the same "content" array or in multiple "user" messages, experiments say. With this change, we are sending them in one "user" message.

The image encoding for OpenAI is the same as for Azure.

Ollama wants to get images in a different format:

{
  "model": "llava",
  "messages": [
    {
      "role": "user",
      "content": "what is in this image?",
      "images": ["{base64_image}"]
    }
  ]
}