Refactor login flow

[jbriones1]

• closes Update auth API routes with /api in mind #88: CORS and redirects using the origin requires the host be supplied
• closes Use search params for the redirect URL (auth) #35: Redirect URL/URI should be supplied in full, will look into fragments later
• closes Only pass session id cookie to api #65: Always send the cookie, since we restrict our API to only certain origins and we currently only ask the backend for API requests since we use a bunch of SPA apps
• closes Update /auth/login to be POST instead of GET #91: Request parameters are now stored in the body.
• closes Refactor login flow #113 (main focus): Refactored the login flow, to match what was explained in the issue

[p-north]

-Mainly looks good. Consider the suggestions and minor tweaks here and there.

[p-north]

-Looks Good!