Updated developer guide

doc/developer_guide/developer_guide.md

@@ -15,3 +15,21 @@ In order to regenerate the model layer please use the following command line:
 ```shell
 poetry run nox generate-api
 ```
+
+### Change the Source URL of API Model JSON Definition
+
+If you want to retrieve the JSON definition for the API model from a different
+source then just edit file `noxfile.py`.
+
+Candidates
+* https://cloud.exasol.com/openapi.json
+* https://cloud-staging.exasol.com/openapi.json
+* https://cloud-staging.exasol.com/internal-api.json
+
+### Read JSON definition From a Local File
+
+Use CLI option `--path` to read the JSON definition from a local file instead of a URL:
+
+```python
+"--path", "/path/to/openapi.json",
+```