Spring-ai Support for Mistral AI - Nineya|java/go/python

Mistral AI develops open-source and secure generative artificial intelligence models.

Mistral is a powerful and fast model, adaptable to many use cases.

Looking at the number of models supported by Spring AI, we'd like it to support Mistral too.

Here are the contents of the PR : * Mistral AI embedding client implementation and Tests class * Mistral AI Chat completion and with streaming and Test class * Mistral AI autoconfiguration and Test class * Mistral AI starter

Comment From: tzolov

@ricken07 thank you for your valuable contribution.

Would be interested to follow up and contribute the Mistral documentation in a separate PR after this is merged? ?
https://github.com/spring-projects/spring-ai/issues/370

You can use the OpenAI docs as a reference.

Comment From: tzolov

Rebased, squashed and some additional changes applied:

 - Add missing license headers.
 - Fix the intialization of default options.
 - Code re-formatting to improve the readability.
 - Many improvements
 - Add missing sine annotations
 - Remove stream field from MistralAiChatOptions. This handled internally.
 - Add MistralAiApi ChatModel and EmbeddingModel enums.
 - Add MistralChatClientIT for testeing chat, stream , parsers...
 - Add MistralAiApiIT tests
 - Refactor and streamline the MistralAiAutoConfiguration.
 - Add MistralAiAutoConfigurationIT

Merged with: 30c3530561db22e11414d26cf04f3ad4db439dec and 16090a96045c004fe0057cc36b1d7dcdf5cc5a56