feat: add hdds/temps/version to display

* Write a mock ustorage tool to parse disk info for ulcmd
* Pass system temp info from unvr-fan-daemon to mock-ubnt-api via tmp file
* add mock ubnt-tools to make ulcmd happy and report our SN
* code cleanup and documentation update

overlay/filesystem/usr/lib/python3/dist-packages/ubnthelpers.py

@@ -0,0 +1,21 @@
+#!/usr/bin/python3
+from functools import lru_cache
+
+"""
+A handful of Ubiquiti Unifi device specific functions
+"""
+
+UBNTHAL_PATH = "/proc/ubnthal/system.info"
+
+
+@lru_cache(None)
+def get_ubnt_shortname() -> str:
+    try:
+        with open(UBNTHAL_PATH, "r") as f:
+            ubnthal_model = [i for i in f.readlines() if i.startswith("shortname=")][0]
+        return ubnthal_model.lstrip("shortname=").rstrip("\n")
+    except FileNotFoundError:
+        print(
+            f"Error: unable to open {UBNTHAL_PATH}; is the ubnthal kernel module loaded?!"
+        )
+        raise