Add support for SSO authentication

Problem to solve

Actually, the only way to login is to use the application-secret (or an API token generated with it).

Proposal

Allow user to configure SSO authentication (we need to chose between OIDC or SAML)

It should :

• Be activated with a feature flag (env var)
  • Disabled by default
  • If deactivated, application-secret should work
• Configuration should be done with environment variables