DOC: Add documentation for hiding/showing of properties

src/doc/extension/display_of_properties.rst

+Tweaking the display of properties
+==================================
+
+Hide or show properties for specific roles and users
+****************************************************
+
+.. note::
+
+   This feature is part of CaosDB WebUI 0.10 and is not available for 0.9.X or
+   older.
+
+.. warning::
+
+   Hiding properties is purely cosmetics and should **never** be considered a
+   security feature. The hidden properties are still part of the server
+   response.
+
+Sometimes it is desirable to hide certain properties for specific users or
+roles, e.g., when they might be irrelevant or confusing. For example, an
+internal id might only be of interest to curators or administrators, whereas it
+is entirely meaningless to most other users.
+
+To configure the hiding of properties, you first need to enable the build
+variable ``BUILD_MODULE_EXT_PROPERTY_DISPLAY``. Then, the display of the
+properties is configured in ``conf/ext/json/ext_prop_display.json``. In there,
+properties of a specific RecordType can be hidden by specifying the name of the
+property, and the names of the roles and/or users from whom it should be hidden.
+
+.. code-block:: json
+
+   {
+     "RecordTypeName": {
+       "hide": [
+         {
+           "name": "property name",
+           "roles": ["list", "of", "roles"],
+           "users": ["list", "of", "users"]
+         },
+         ...
+       ]
+     },
+     ...
+   }
+
+In the same way but using the ``show`` keyword, properties can be hidden for
+everyone **but** the specified users/roles:
+
+.. code-block:: json
+
+   {
+     "RecordTypeName": {
+       "show": [
+         {
+           "name": "property name",
+           "roles": ["list", "of", "roles"],
+           "users": ["list", "of", "users"]
+         },
+         ...
+       ]
+     },
+     ...
+   }
+ 
+
+For example, using the data from demo.indiscale.com, the following would hide
+the ``price`` of all ``MusicalInstruments`` from ``anonymous`` and their
+``Manufacturer`` from the ``admin`` user.
+
+.. code-block:: json
+
+   {
+     "MusicalInstrument": {
+       "hide": [
+         {"name": "price", "roles": ["anonymous"], "users": []},
+         {"name": "Manufacturer", "roles": [], "users": ["admin"]}
+       ]
+     }
+   }
+
+Future
+******
+
+In the future, this feature will be extended to allow the RecordType-wise
+`sorting <https://gitlab.com/caosdb/caosdb-webui/-/issues/189>`__ of properties
+and to `toggle <https://gitlab.com/caosdb/caosdb-webui/-/issues/190>`__
+properties.