Add common childsetup interface (#1470)

Add a common interface for the `childsetup` module across `smart` and `smartcam` hubs.
Co-authored-by: Teemu R. <tpr@iki.fi>

kasa/interfaces/childsetup.py

@@ -0,0 +1,70 @@
+"""Module for childsetup interface.
+
+The childsetup module allows pairing and unpairing of supported child device types to
+hubs.
+
+>>> from kasa import Discover, Module, LightState
+>>>
+>>> dev = await Discover.discover_single(
+>>>     "127.0.0.6",
+>>>     username="user@example.com",
+>>>     password="great_password"
+>>> )
+>>> await dev.update()
+>>> print(dev.alias)
+Tapo Hub
+
+>>> childsetup = dev.modules[Module.ChildSetup]
+>>> childsetup.supported_categories
+['camera', 'subg.trv', 'subg.trigger', 'subg.plugswitch']
+
+Put child devices in pairing mode.
+The hub will pair with all supported devices in pairing mode:
+
+>>> added = await childsetup.pair()
+>>> added
+[{'device_id': 'SCRUBBED_CHILD_DEVICE_ID_5', 'category': 'subg.trigger.button', \
+'device_model': 'S200B', 'name': 'I01BU0tFRF9OQU1FIw===='}]
+
+>>> for child in dev.children:
+>>>     print(f"{child.device_id} - {child.model}")
+SCRUBBED_CHILD_DEVICE_ID_1 - T310
+SCRUBBED_CHILD_DEVICE_ID_2 - T315
+SCRUBBED_CHILD_DEVICE_ID_3 - T110
+SCRUBBED_CHILD_DEVICE_ID_4 - S200B
+SCRUBBED_CHILD_DEVICE_ID_5 - S200B
+
+Unpair with the child `device_id`:
+
+>>> await childsetup.unpair("SCRUBBED_CHILD_DEVICE_ID_4")
+>>> for child in dev.children:
+>>>     print(f"{child.device_id} - {child.model}")
+SCRUBBED_CHILD_DEVICE_ID_1 - T310
+SCRUBBED_CHILD_DEVICE_ID_2 - T315
+SCRUBBED_CHILD_DEVICE_ID_3 - T110
+SCRUBBED_CHILD_DEVICE_ID_5 - S200B
+
+"""
+
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+
+from ..module import Module
+
+
+class ChildSetup(Module, ABC):
+    """Interface for child setup on hubs."""
+
+    @property
+    @abstractmethod
+    def supported_categories(self) -> list[str]:
+        """Supported child device categories."""
+
+    @abstractmethod
+    async def pair(self, *, timeout: int = 10) -> list[dict]:
+        """Scan for new devices and pair them."""
+
+    @abstractmethod
+    async def unpair(self, device_id: str) -> dict:
+        """Remove device from the hub."""