Handling of binding requests

[DerAndereAndi]

Right now we have at least these issues with handing of bindings:

• All usecase client implementations ignore if bindings are rejected and continue as if they would be granted. There is no error handling to the application side
• The spine-go implementation only allows 1 binding per server feature on an entity. This is the safe approach but we need to consider the following additional scenarios:
  • the first binding request wins  
  • the "wrong" device may have been the one with the first binding (e.g. CEM vs SMGW)

Therefor we may need:

• a way for an application to define which device may get the binding
• delete existing bindings and tell the device about this
• handle this scenario in our usecase client side implementations as well
• Handle that some devices may continue to request bindings when they didn't get them approved

There may be more

[DerAndereAndi]

E.g. with LPC and LPP as Controllable System, we could automatically detect an SMGW when SHIP Pairing was used. In all other scenarios the user of the device has to device. This is because we can't identify an SMGW over an also connected CEM in any other way. SMGWs do not use the entity type gridguard but use cem instead. Whysoever.

Also what happens if 2 CEM devices are paired. We know from experience that end users will pair any device with any other. Just because they can. But any given usecase only works with a single device pair only. If the stack does something automatically, it most likely will be wrong. We need a good concept, because EEBUS does not have one itself. It is defined nowhere.