Make the LCT SECIR model a derived class of FlowModel

[lenaploetzke]

Motivation / Current Behaviour

At the moment, the LCT SECIR model is a derived class of CompartmentalModel which is the base class of FlowModel.

Enhancement description

Make the LCT SECIR model a derived class of FlowModel instead of CompartmentalModel. This would have the advantage that the flows could be used. Inheritance from the flow model is required for a model with mobility.

Additional context

Checklist

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

[lenaploetzke]

My problem with this is, that for lct_populations, it makes no sense to have a type Index as we want to have different substates for different groups (important). (Therefore, we do not inherit from CustomIndexArray.) This Index is required for FlowModel.

Moreover, i think, we need flow values in between the subcompartments. Therefore, it is not possible to hard-code the Flows as for the other FlowModels. One solution could be to write an own class LctFlowModel?