Display Workflows and save as file

[PProfizi]

Proposal for a Workflow viewer in PyDPF.
This uses graphviz rendering and the native system image viewer to show the image obtained with graphviz.

To be discussed.

[codecov]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (6bddcba) 87.98% compared to head (6606139) 87.80%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1300      +/-   ##
==========================================
- Coverage   87.98%   87.80%   -0.19%     
==========================================
  Files          81       81              
  Lines        9482     9506      +24     
==========================================
+ Hits         8343     8347       +4     
- Misses       1139     1159      +20     

[rafacanton]

Generic comment: although I have the graphviz Python dependency in the venv, this was not enough to render the image. It raised this error: graphviz.backend.execute.ExecutableNotFound: failed to execute WindowsPath('dot'), make sure the Graphviz executables are on your systems' PATH, so I needed to manually install graphviz from here. If we want this out the box, maybe we need an additional dependency that installs graphviz server.

[rafacanton]

same here

[rafacanton]

This is what I get with (viewer="paraview"):

[PProfizi]

@FedericoNegri

[PProfizi]

This is what I get with (viewer="paraview"):

I removed the PyVista viewer as it had no added value and just made everything more complicated.

[PProfizi]

Generic comment: although I have the graphviz Python dependency in the venv, this was not enough to render the image. It raised this error: graphviz.backend.execute.ExecutableNotFound: failed to execute WindowsPath('dot'), make sure the Graphviz executables are on your systems' PATH, so I needed to manually install graphviz from here. If we want this out the box, maybe we need an additional dependency that installs graphviz server.

Added the requirement to the dosctring