Tutorial on how to create general fluid objects for porepy models.

[vlipovac]

Related to #1240 , the fluid attribute in pp models will be a more general object, involving a phase and component context (see PR #1252 )

A tutorial is required explaining the respective FluidMixin and the main methods which user can override to create a custom fluid:

• get_components
• get_phase_configuration

as well as the respective objects Component, Phase, PhysicalState and EquationOfState. The latter one should be covered briefly because it requires an own tutorial anyways.

The second part of the tutorial should also cover a deeper dive into setting up complex fluids for CF simulations involving correlations or equilibrium calculations. It involves the mixed-in methods:

• set_components_in_phases
• dependencies_of_phase_properties
• and various factories for phase properties like density_of_phase