[Docs] Update environment docs for developing own apps

docs/dev/02_install_apps.rst

@@ -9,6 +9,26 @@ sub-folder of the meta repository. If you followed the documentation, they
 will already be checked out in the version required for the bundle you
 are running.
 
+Installing a development environment for own apps
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you are developing your own app, you probably do not want to
+ru na development environment from the `AlekSIS-Core` repository.
+
+Instead, simply install the environment using ``poetry install`` from
+your app repository – it will pull in `AlekSIS-Core` as a dependency
+automatically, and everything will work as described beforehand.
+
+.. note::
+   Take care not to mix up environments, especially if using ``poetry shell``.
+
+
+Using one virtual environment for everything
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. note::
+   This method is not encouraged for most use cases.
+
 Installing apps into the existing virtual environment of `AlekSIS-Core` can
 be easily done after starting `poetry shell`::
 
@@ -17,5 +37,6 @@ be easily done after starting `poetry shell`::
 Do not forget to run the maintenance tasks described earlier after
 installing any app.
 
-**Heads up:** This is not suitable for working on the core, because it
-will install the `AlekSIS-Core` version used by the app using `pip` again.
+.. note::
+   This is not suitable for working on the core, because it
+   will install the `AlekSIS-Core` version used by the app using `pip` again.