Move transports into their own package (#1247)

This moves all transport implementations into a new `transports` package
for cleaner main package & easier to understand project structure.

kasa/transports/basetransport.py

@@ -0,0 +1,55 @@
+"""Base class for all transport implementations.
+
+All transport classes must derive from this to implement the common interface.
+"""
+
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from kasa import DeviceConfig
+
+
+class BaseTransport(ABC):
+    """Base class for all TP-Link protocol transports."""
+
+    DEFAULT_TIMEOUT = 5
+
+    def __init__(
+        self,
+        *,
+        config: DeviceConfig,
+    ) -> None:
+        """Create a protocol object."""
+        self._config = config
+        self._host = config.host
+        self._port = config.port_override or self.default_port
+        self._credentials = config.credentials
+        self._credentials_hash = config.credentials_hash
+        if not config.timeout:
+            config.timeout = self.DEFAULT_TIMEOUT
+        self._timeout = config.timeout
+
+    @property
+    @abstractmethod
+    def default_port(self) -> int:
+        """The default port for the transport."""
+
+    @property
+    @abstractmethod
+    def credentials_hash(self) -> str | None:
+        """The hashed credentials used by the transport."""
+
+    @abstractmethod
+    async def send(self, request: str) -> dict:
+        """Send a message to the device and return a response."""
+
+    @abstractmethod
+    async def close(self) -> None:
+        """Close the transport.  Abstract method to be overriden."""
+
+    @abstractmethod
+    async def reset(self) -> None:
+        """Reset internal state."""