* move forward_at_cmd_resp into InfosG3P class
- the variable is shared between the two connections
of an inverter. One is for the TSUN cloud and the
other for the device.
* use inverter class to share values between
the two protocol instances of a proxy
- move forward_at_cmd_resp into class InverterG3P
- store inverter ptr in Solarman_V5 instances
- add inverter ptr to all constructurs of protocols
- adapt doku and unit tests-
- add integration tests for AT+ commands which
check the forwarding from and to the TSUN cloud
* adapt and improve the unit tests
- fix node_id declaration, which always has a / at
the end. See config grammar for this rule
- set global var test to default after test run
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