Replace snake_casing with camelCasing

[namsnath]

A lot of places in the codebase use snake_casing, which is not consistent with the rest of the code. These could be replaced with camelCased names to adhere to JS naming conventions.

Examples:
User Model
Course Model

Changes to these will require changes in places in the frontend as well as the backend.

This is a significant refactor spanning multiple files in both the frontend and the backend.

[dannyflatiron]

I just created a PR for this, hope it helps!

[namsnath]

I'll assign this to you for now. We can discuss on the PR thread you created (#93).