Error and Audit logger webhooks (#1855)

Similar to MinIO now it's possible to configure webhooks to log all
triggered errors and incomming requests via env variables:

```
CONSOLE_LOGGER_WEBHOOK_ENABLE_<ID>
CONSOLE_LOGGER_WEBHOOK_ENDPOINT_<ID>
CONSOLE_LOGGER_WEBHOOK_AUTH_TOKEN_<ID>
CONSOLE_LOGGER_WEBHOOK_CLIENT_CERT_<ID>
CONSOLE_LOGGER_WEBHOOK_CLIENT_KEY_<ID>
CONSOLE_LOGGER_WEBHOOK_QUEUE_SIZE_<ID>

CONSOLE_AUDIT_WEBHOOK_ENABLE_<ID>
CONSOLE_AUDIT_WEBHOOK_ENDPOINT_<ID>
CONSOLE_AUDIT_WEBHOOK_AUTH_TOKEN_<ID>
CONSOLE_AUDIT_WEBHOOK_CLIENT_CERT_<ID>
CONSOLE_AUDIT_WEBHOOK_QUEUE_SIZE_<ID>
```

Signed-off-by: Lenin Alevski <alevsk.8772@gmail.com>

restapi/admin_users_test.go

@@ -525,7 +525,7 @@ func TestListUsersWithAccessToBucket(t *testing.T) {
 			}
 			return mockResponse, nil
 		}
-		return nil, ErrorGeneric
+		return nil, ErrDefault
 	}
 	type args struct {
 		bucket string