Add debug log when ignoring configured endpoint

Add a debug statement when specifically ignoring the configured
endpoint URL from the shared configuration file or an environment
variable. This will not be logged if the endpoint URL is set through
the client constructor.

botocore/args.py

@@ -267,9 +267,11 @@ def compute_client_args(
         }
 
     def _compute_configured_endpoint_url(self, client_config, endpoint_url):
-        if endpoint_url is not None or self._ignore_configured_endpoint_urls(
-            client_config
-        ):
+        if self._ignore_configured_endpoint_urls(client_config):
+            logger.debug("Ignoring configured endpoint URLs.")
+            return endpoint_url
+
+        if endpoint_url is not None:
             return endpoint_url
 
         return self._config_store.get_config_variable('endpoint_url')