Integrate PHYTOS 31 leaf wetness sensor

[jmadden173]

Describe the Enhancement
Read a voltage measurement from the leaf wetness sensor and upload over LoRa to Dirtviz.

Benefits
Add a new sensor to the platform

Possible Drawbacks
N/A

Additional Context
The scope of the work is the following:

• Measure voltage from the sensor
• Add protobuf message for leaf wetness sensor
• Integrate with sensor library to TX measurements

Will need to coordinate with Dirtviz team to add capabilities to display data.

Also @jmadden173 will update the issue with fields required for the leaf wetness sensor. Currently will just be voltage, but maybe some calibration or offset to convert 24 bit ADC reading to 16 bit to save space. It looks like we only need a 12 bit measurement according to the datasheet.

Link to sensor page: https://metergroup.com/products/phytos-31/
Manual: https://library.metergroup.com/Manuals/20434_PHYTOS31_Manual_Web.pdf
^ the sensor page is broken for me so here's the manual if that's the case

Issues #53 #50 are blockers.

[jmadden173]

Tagging @cjosephson

Caden is going to take a look at this once a sensor is available (invite to Github is in progress). Depending on progress @jmadden173 or @stevegtaylor will assist as needed.

[jmadden173]

I talked with Cristian who's doing the materials aspect of the leaf wetness sensor and it sounds like we should transmit the raw voltage reading and have another field for some future calibrated measurement. I guess both should be doubles after our experience with inconsistent float input parameters?

[jmadden173]

@gxjacobs Steve is working on the 58-integrate-phytos-31-leaf-wetness-sensor this Friday, if you have the free time to work it on it merge from that branch in order to not duplicate work.