Preparing for FarmBeats using node red

Here I demo the use of node-red unit tests in preparation for FarmBeats. It is not a working FarmBeat program but just illustrates the use of node-red using Seeed Studio library for node-red when using the Raspberry Grove HAT. Using this approach it is possible to implement a fully FarmBeats compatible program without using the original python programs on Raspberry Pi. The reason for doing this is that it is easy to develop more complex IoT programs on node-red compared to python.

The hardware here is a Raspberry Pi Model 4 with a Seeed Studio Raspberry Pi Grove HAT. I am using version 1 - the original stand alone version.
Connected to the HAT are a number of Grove devices and all of them are wrapped in Lego wrappers also from Seeed Studio. Almost all of the Grove devices mounted on Lego wrappers are then mounted on Lego base plates which are attached to a Sunfounder board that has the Raspberry Pi mounted and can support other computers such as Arduino Uno and Mega.

Grove cables - each with 4 wires connect each Grove device to the HAT except for the Soil Temperature Probe (a DS18B29 device) and it goes to the
GPIO pins directly where only GPIO 4 (physical pin 7) supports the DS18B20.

I am using the following Grove devices:
* Grove LED
* Grove Relay (original FarmBeats)
* Grove Push Button
* Grove Dual Buttons x 2 (one in original FarmBeats)
* Grove Rotary Sensor (Pot)
* Grove Light - Digital sensor (replaces the Grove Sun in the original FarmBeats)
* Grove Light - Analog sensor
* Grove Air Quality Sensor
* Grove SHT31 sensor (air temperature and humidity) on I2C (replaces the DHT11 in the original FarmBeats)
* Grove Moisture sensor - soil moisture (original FarmBeats)
* Grove DS18B20 - soil temperature sensor (original FarmBeats)

As Seeed Studio has not updated its node-red Raspberry Pi library to be compatible with the current operating system it is necessary to use an older versions of the Raspberry Pi Operating System (Buster)and an older version of node-red (V1.0.3) otherwise the Seeed Studio node-red libraries will node work on the latest operating system (Bullseye).

Three approaches are used in the node-red program using:
* direct GPIO nodes for digital GPIO devices: Dual Buttons. The Seeed Studio Raspberry HAT for Grove routes the digital & I2C GPIO signals direct to the Raspberry Pi GPIO signals. It is a different matter for Analog where the Raspberry Pi does not have native analog GPIO pins.
* Linux shell node for the Seeed Studio python shell libraries - examples for rotary angle sensor (pot) and soil moisture sensor. A 'exec' node is used for this with a time out for a spawned shell of 0.2 secs to kill the process. There are even more python scripts to explore here.
* Seeed Studio node-red nodes - most of the Grove devices but not all of the original FarmBeats Grove devices are supported. You will have to replace the Grove Sun sensor with a Grove Digital Light sensor.

To do additional work for FarmBeats the message payloads for the sensor nodes still need to be parsed and then combined in a single CSV payload ready to be inserted into a MQTT node.