Convert message options to seperate class

[chiouyazo]

See here for available options: https://github.com/jmorganca/ollama/blob/main/docs/modelfile.md#valid-parameters-and-values

The options are currently just a string, which is... not optimal
It should rather be a class which has all available options.
So you can set them easier, and then only the ones which arent null get parsed into the request

[chiouyazo]

Implemented in #15