clan-app: Move middleware to it's own folder

pkgs/clan-app/clan_app/middleware/base.py

@@ -0,0 +1,31 @@
+from abc import ABC, abstractmethod
+from contextlib import AbstractContextManager, ExitStack
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from clan_app.api.api_bridge import ApiBridge, BackendRequest
+
+
+@dataclass
+class MiddlewareContext:
+    request: "BackendRequest"
+    bridge: "ApiBridge"
+    exit_stack: ExitStack
+
+
+@dataclass(frozen=True)
+class Middleware(ABC):
+    """Abstract base class for middleware components."""
+
+    @abstractmethod
+    def process(self, context: MiddlewareContext) -> None:
+        """Process the request through this middleware."""
+
+    def register_context_manager(
+        self,
+        context: MiddlewareContext,
+        cm: AbstractContextManager[Any],
+    ) -> Any:
+        """Register a context manager with the exit stack."""
+        return context.exit_stack.enter_context(cm)