development: how to add extensions

Author: Pablo Panero

docs/develop/customize.md

@@ -23,3 +23,5 @@ Go to the browser [*https://localhost:5000/*](https://localhost:5000) or refresh
 
 !!! warning "That evil cache"
     If you do not see it changing, check in an incognito window, the browser might have cached the logo.
+
+Need further customizations? Have you thought of creating your own extensions? How to add them to your InvenioRDM instance is explained in the next section - [here](../extensions/custom.md).

docs/extensions/custom.md

@@ -0,0 +1,60 @@
+# Extensions
+
+If you need to add custom functionalaty to your RDM instance you need to develop your own module. You can start it by using the [cookiecutter-invenio-module](https://github.com/inveniosoftware/cookiecutter-invenio-module) template. It will get you started in no time.
+
+## Create your module
+Lets assume you have already done so:
+
+``` console
+$ cookiecutter https://github.com/inveniosoftware/cookiecutter-invenio-module
+
+[...]
+```
+
+## Add your functionality
+
+And you have added a simple view to the blue print in the `<your_custom_module>/views.py`, which looks like:
+
+``` python
+[...]
+blueprint = Blueprint(
+    'invenio_rdm_extension_demo',
+    __name__
+)
+
+
+@blueprint.route("/rdm-ext-demo")
+def index():
+    """RDM Extension Demo view."""
+    return 'RDM Extension Demo!'
+```
+
+## Integrate it in your InvenioRDM instance
+
+Once you have your functionality ready, in order to add it to your instance you just have to install the module via pipenv:
+
+``` console
+$ cd path/to/your/instance
+$ pipenv install [--pre] -e path/to/your/extension
+```
+
+As you can see, `--pre` is optional, it is only needed when the package is in a pre-release state. In addition, note that you do not need to specify a local path, if the package is available e.g. via PyPi you can just install it by its name.
+
+## Sanity check and run!
+
+Check that the Pipfile got a new line with your extension. For example:
+
+``` console
+...
+
+[packages]
+...
+invenio-rdm-extension-demo = {editable = true, path="../invenio-rdm-ext-demo"}
+...
+```
+
+It's all set, run your instance with the cli and you will have your new features available!
+
+``` console
+$ invenio-cli run
+```

mkdocs.yml

@@ -36,6 +36,8 @@ nav:
     - Customization: 'develop/customize.md'
     - Troubleshooting: 'develop/troubleshoot.md'
     - Cleanup: 'develop/cleanup.md'
+  - Extensions:
+    - Add your extensions: 'extensions/custom.md'
   - Deploy:
     - Kubernetes: 'deployment/kubernetes.md'
     - OpenShift: 'deployment/openshift.md'