Add and configure drf-spectacular

[rachellougee]

Description/Context

MIT open uses drf-spectacular to generates OpenAPI spec from Django views. @JenniWhitman recommended it for MITx Online as it comes with some features that don't exist in Django rest framework.

Once drf-spectacular is installed, it should works out of the box, but also provides ways to customize the generated OpenAPI schema. Per their docs, It is explicitly designed to work well for documentation (SwaggerUI, ReDoc).

Plan/Design

• Add drf-spectacular to tool.poetry.dependencies
• Config DRF Spectacular settings (similar to MIT Open's settings_spectacular)
• Add SwaggerUI and ReDoc (similar to https://github.com/mitodl/mit-open/blob/main/learning_resources/urls.py#L53-L64)
• Any helpers to get drf-spectacular to work with our MITx Online django rest api

Note that the existing API won't need to be touched, but if any docstring needs to be updated, please feel free to do so