Reduced steps for local development setup for social media auth (#1374) (#1383)

This is related to ticket #1374, and simplifies the steps for local
development environments to have a working login flow for github and
google.

The improvements were configuration for the client id and secret for
google and github via .env vars instead of having to go through setting
up "Social Applications" via the admin interface, and automating the
process for creating google cloud projects in which oauth clients can be
created. Documentation was adjusted to fit.

That was as far as this could be automated given limitations on both
Google Cloud Platform and Github's APIs for creating oauth clients/apps.

The terraform process can be improved if these tickets see some progress
or an API comes about to support this.

Google
https://github.com/hashicorp/terraform-provider-google/issues/16452
https://issuetracker.google.com/issues/116182848

Github
https://github.com/integrations/terraform-provider-github/issues/786

config/settings.py

@@ -348,8 +348,37 @@ SOCIALACCOUNT_PROVIDERS = {
             "access_type": "online",
         },
         "OAUTH_PKCE_ENABLED": True,
-    }
+    },
+    "github": {},
 }
+if LOCAL_DEVELOPMENT:
+    github_oauth_client_id = env("GITHUB_OAUTH_CLIENT_ID", default=None)
+    github_oauth_secret = env("GITHUB_OAUTH_CLIENT_SECRET", default=None)
+    if not github_oauth_client_id or not github_oauth_secret:
+        logging.warning("Github OAuth credentials not set")
+    else:
+        SOCIALACCOUNT_PROVIDERS["github"] = {
+            "APPS": [
+                {
+                    "client_id": github_oauth_client_id,
+                    "secret": github_oauth_secret,
+                }
+            ]
+        }
+    google_oauth_client_id = env("GOOGLE_OAUTH_CLIENT_ID", default=None)
+    google_oauth_secret = env("GOOGLE_OAUTH_CLIENT_SECRET", default=None)
+    if not google_oauth_client_id or not google_oauth_secret:
+        logging.warning("Google OAuth credentials not set")
+    else:
+        SOCIALACCOUNT_PROVIDERS["google"] = {
+            "APPS": [
+                {
+                    "client_id": google_oauth_client_id,
+                    "secret": google_oauth_secret,
+                }
+            ]
+        }
+
 
 # Allow Allauth to use HTTPS when deployed but HTTP for local dev
 SECURE_PROXY_SSL_HEADER_NAME = env("SECURE_PROXY_SSL_HEADER_NAME", default=None)