Add Google OAuth2 based authentication

[varun-r-mallya]

Google Authentication complete
Problems:

• Hash and Salt fields are still there. Not removed yet.
• Google Authentication credentials are committed due to issues in environment variables.

Documentation:
Authentication routes and pipeline configuration.

Routes

The /auth scope handles authentication-related endpoints:
* GET /auth/ping - Basic connectivity check
* GET /auth/google - Initiates Google OAuth flow (To test, on your browser, visit localhost:4000/auth/google)
* GET /auth/google/callback - Handles Google OAuth callback (Frontend people don't have to deal with this)
* GET /auth/logout - Handles user logout (Just GET this to logout)

Pipeline

The :authenticated_api pipeline provides authentication middleware:
* Accepts JSON requests
* Enables session handling
* Authenticates requests via AuthPlug

NOTES:
Automatically adds cookie to the browser and does auth check

[varun-r-mallya]

Merge pls :)

[rizul2108]

@Darkhood148 you also review works fine from my side

[Darkhood148]

Dotenv k alava env reader dependencies hta do. Then merge. GTG mere side se
@varun-r-mallya

[varun-r-mallya]

@Darkhood148 @rizul2108