Generalize class for optimization problems to arbitrary FlowModels

[lenaploetzke]

Motivation / Current Behaviour

PR #895 implements the example "cpp/examples/ode_seair_optimization.cpp" for solving an optimization problem for a SEAIR model. The implemented class is currently not tested.

Enhancement description

The example should be moved to another location where the functionality can be tested. It should also be possible to generalize the implemented class to define an optimization problem for any FlowModel.

Additional context

No response

Checklist

• [X] Attached labels, especially loc:: or model:: labels.
• [X] Linked to project