Separating out setting model type into a separate method in the job service

[veekaybee]

What's changing

We currently have a lot going on in the create_job method which makes it hard to unit test granularly. We've previously done some work in pulling out separate methods (see https://github.com/mozilla-ai/lumigator/pull/328), this PR does the same for _set_model_type and adds tests also clarifying the model URL (it wouldn't be S3 since we use either huggingface, openai or mistral at the moment) in the SDK.

How to test it

Run unit tests

Additional notes for reviewers

I already...

• [X] added some tests for any new functionality
• [ ] updated the documentation
• [ ] checked if a (backend) DB migration step was required and included it if required

cc @peteski22 @javiermtorres fyi for SDK changes

[veekaybee]

Also adding ruff precommit hooks here because they're not getting caught before they reach the linter in CI