Google and generic OIDC sign-in

Hive supports sign-in through multiple identity providers at the same time. Google is built in and can be configured with HIVE_GOOGLE_CLIENT_ID, HIVE_GOOGLE_CLIENT_SECRET, and an optional HIVE_GOOGLE_ALLOWED_DOMAINS allowlist. You can also add any generic OpenID Connect provider via HIVE_OIDC_ISSUER, HIVE_OIDC_CLIENT_ID, HIVE_OIDC_CLIENT_SECRET, and HIVE_OIDC_DISPLAY_NAME. The login page renders a button for each configured provider, and Ueberauth handles the OIDC flow. (https://github.com/tuist/hive/pull/1, https://raw.githubusercontent.com/tuist/hive/server@0.2.0/lib/hive/auth.ex, https://raw.githubusercontent.com/tuist/hive/server@0.2.0/config/runtime.exs, https://raw.githubusercontent.com/tuist/hive/server@0.2.0/lib/hive_web/auth_controller.ex, https://raw.githubusercontent.com/tuist/h