generate_embeddings management command

[alex-nork]

The purpose of this PR is to add a management command called generate_embeddings. It allows the user to easily select
the embedding model service, and based on their selection the user is presented with the available embedding models. Once the user provides their username and password, the API key provided for the selected service is used to generating the embeddings.

[zimventures]

The approach here feels like it may cause some problems down the road.

Instead of writing the fixture data to an intermediary fixture, then loading that fixture - what about writing the data directly to the database, then using the dumpdata command to export the fixtures?

Notably - the logic where data_to_write is built, is very subject to breakage if the schema changes.

thinking out loud
It's a shame we can't use the existing embedding provider classes to perform the embedding (as opposed to importing the libraries here and doing them). It's not really doable because the providers need a user object...

[zimventures]

FANTASTIC! Really great stuff. Excellent use of the prompts to employ an existing user.