Feature Request: support `"encoding_format": "base64"` in the `*/embeddings` endpoints

[ggerganov]

Prerequisites

• I am running the latest code. Mention the version if possible as well.
• I carefully followed the README.md.
• I searched using keywords relevant to my issue to make sure that I am creating a new issue that is not already open (or closed).
• I reviewed the Discussions, and have a new and useful enhancement to share.

Feature Description

The OpenAI embeddings API supports returning the embeddings in base64 format:

https://platform.openai.com/docs/api-reference/embeddings/create#embeddings-create-encoding_format

We should implement this option in the server and enable it both for the /v1/embeddings and /embeddings endpoints.

Motivation

Reduce JSON payload and increase OAI compatibility.

Possible Implementation

No response