UPF capabilities

[germa89]

UPF capabilities are not checked. I am not sure they work.

Launch Docker with UPF capabilities
===================================

If you want to specify a custom Python UPF routine, you must have the
environment variables ``ANS_USER_PATH`` and ``ANS_USE_UPF`` defined. The
former should be equal to the path where the UPF routines are located, and the
latter should be equal to ``TRUE``.

In WSL, you can do this using:

.. code:: bash

    export ANS_USER_PATH=/home/user/UPFs # Use your own path to your UPF files.
    export ANS_USE_UPF=TRUE

You can then run the Docker image with:

.. code:: bash

    docker run -e [email protected] -e ANS_USER_PATH='/ansys_jobs/upf' -e ANS_USE_UPF='TRUE' --restart always --name mapdl -p 50053:50052 ghcr.io/pyansys/pymapdl/mapdl -smp  1>log.txt

.. warning:: The use of UPFs with Docker images or PyMAPDL is still in the alpha state.