Add abstract monitor handler

Because:
 - provide common functionality of monitor observer. USB and Monitor
    handlers will be implemented later.

src/scripts/python/Handler.py

@@ -0,0 +1,46 @@
+from abc import ABC, abstractmethod
+from pyudev import Context, Monitor, MonitorObserver
+
+
+class Handler(ABC):
+    """Abstract Handler calss for device monitoring
+
+    NOTE: No checking are done for overlaping filters and callback will be
+    even by multiple handlers.
+
+    Args:
+        ABC: Abstract Base Class, provides abstract method functionality and
+             readability.
+    """
+
+    def __init__(self, filter) -> None:
+        """Initiate a monitor observer and applies `filter` if any provided
+
+        Args:
+            filter (_type_): _description_
+        """
+        monitor = Monitor.from_netlink(Context())
+        if filter:
+            monitor.filter_by(filter)
+        self.observer = MonitorObserver(monitor, callback=self.handler)
+        self.observer.start()
+
+    @abstractmethod
+    def callback(self, device):
+        """Callback
+
+        This method must be implemented by child calsses. This method is
+        responsible for further managments of the devices related to its filter.
+
+        Args:
+            device (pyudev.Device): device passed by observer through handler
+        """
+        raise NotImplemented("Callback MUST be implemented")
+
+    def handler(self, device):
+        """wrapper around callback implemented
+
+        Args:
+            device (pyudev.Device): modified device passed by self.observer
+        """
+        self.callback(device)