This PR adds support to control the external power output from controllers like nice!nano, nRFMicro etc
I have implemented based on my understanding of Pete suggestion on this feature.
Testing done:
Tested by enabling and disabling the ext_power from application and verified
Verified the application does not crash with boards that does not have ext_power support
Note:
I did not test this in nice!nano since I don't have the boards. Will get help from others once the behavior PR is up
Next Steps:
Create a behavior PR to control enable/disable ext_power
