DOC: add doc on serverside

Please test examples.

src/doc/tutorials/serverside.rst

+
+Server Side Scripting
+=====================
+
+The administrator may store regularly needed scripts, e.g. for computing a
+standardized analysis, on the same machine as the CaosDB server, "on the server
+side", where they can be run directly by the server.
+
+The execution of those scripts can be initiated using the Python client, or the
+web interface.
+
+Call a Script
+~~~~~~~~~~~~~
+
+If you have access to the server and sufficient permissions to run the script,
+execution is fairly simple:
+
+.. code:: python
+
+    from caosdb.utils.server_side_scripting import run_server_side_script
+    response = run_server_side_script('scriptname.py')
+    print(response.stderr,response.stdout)
+
+
+This makes the server run the script ``scriptname.py``. The output of the
+script (``stderr`` and ``stdout``) is returned within an response object.
+
+
+If the script requires additional arguments, those can be provided after the 
+script's name.
+
+Note that by default the script runs with your CaosDB account. It has your
+permissions and changes are logged as if they were done by you directly.
+
+
+Testing it
+~~~~~~~~~~
+
+You can try this out using for example the ``diagnostics.py`` script (it is part
+of the `CaosDB server repository
+<https://gitlab.indiscale.com/caosdb/src/caosdb-server/-/blob/main/scripting/bin/administration/diagnostics.py>`_
+and is also available on https://demo.indiscale.com). The script returns
+information about the server in JSON format. You can do for example the
+following:
+
+.. code:: python
+
+    import json
+    from caosdb.utils.server_side_scripting import run_server_side_script
+    response = run_server_side_script('administration/diagnostics.py')
+    print("JSON content:")
+    print(json.loads(response.stdout))
+    print("stderr:")
+    print(response.stderr)
+
+
+Further Information
+~~~~~~~~~~~~~~~~~~~
+
+Additionally, you might want to have a look at
+https://docs.indiscale.com/caosdb-server/specification/Server-side-scripting.html