Concept for variables that are input and output

[chrbertsch]

citing from: https://github.com/modelica/fmi-design/tree/master/Meetings/2023/2023-01-17-FMI-Design-Webmeeting

Clocked variables: input and output?
Pierre: not possible in FMI 3
Andreas: We need two variables. We need an issue for this.
Christian: is this not a special kind of terminal?
Pierre: might be similar for acausal connections? We could look for a general solution

Currently https://github.com/modelica/fmi-ls-bus/blob/main/docs/2____common_concepts.adoc reads:

If an FMU represents network nodes that are both sender and receiver of a signal, the receiver role will be removed from the FMU interface to allow the signals to have a unique role as output and the reading of such outputs must be handled internally to the FMU.
[The FMI standard requires a variable to be either input or output.]
TODO: is this correct? does that also work for network simulations? how else to solve this unique-variable-name requirement?

[chrbertsch]

Is this problem in the high cut not similar to the Tx / Rx approach in the low cut?
Do we need a duplication of variables (one input and one output, e.g., SignalName_IN, SignalName_OUT, or Signalanme_Tx, SignalName_Rx?)