[feature] add an embedding provider for a new model

[hsluoyz]

The already supported embedding provider list can be found at: https://github.com/casibase/casibase/tree/master/embedding . Feel free to choose a new model which is not on the list.

Both frontend and backend code need to be added to support a new embedding provider

See previous similar PRs: https://github.com/casibase/casibase/issues?q=is%3Aissue+is%3Aclosed+embedding+provider

See online demo: https://demo-admin.casibase.com/providers/provider_embedding_openai_v3