Avoid similar name confusion between autogenerated files and client wrappers

Juno's SDK primarily consists of two parts:
- The autogenerated files from OpenAPI
- Wrappers for each service to handle validation, authentication, etc.

However, these two files have very similar names:
- `Api` (autogenerated) vs `API` (wrapper)

This can especially be confusing if we're doing any sort of documentation generation:

As such, we'll likely need to switch the wrapper classes to a name other than an API suffix. One idea might be changing it to `Client` for wrappers:
- `EmailClient`
- `AuthClient`
- `UserClient`
- ...etc.

Locate the autogenerated Api files and the corresponding API wrapper classes, then trace their references in the SDK and documentation-generation setup. Confirm the replacement naming convention with maintainers before changing names. Done means wrapper and generated names are unambiguous and all affected references and documentation use the agreed convention.

Written by the indexing model from the issue text.