Implement oAuth credentials as environment variables

[SanketDG]

Description

As a developer or someone who sets up the application,
I would want to easily set up the oAuth integrations that are already implemented.

Currently, given how django-allauth works by default, one has to go into the admin console
and create new oAuth apps.

Using settings.py for the application credentials is also supported by django-allauth and this aligns with https://12factor.net/config, so we should go ahead and implement that and load the settings through respective environment variables.

Definition of Done

• Find all the oAuth Integrations used in this project.
• For each oAuth integration, read credentials from the environment through settings.
• Approval by 1 mentor.

Estimation

24 hours

[satya7289]

Do credentials for all type of Auth variables need in config file like Facebook, Google, slack etc.
@SanketDG

[SanketDG]

@satya7289 Nope, only the ones we have, see https://github.com/anitab-org/portal/blob/develop/systers_portal/templates/account/signup.html