feat: add CompositeAsyncHandler to support multiple handlers

src/ldp/http/RequestParser.ts

@@ -5,4 +5,4 @@ import { Operation } from '../operations/Operation';
 /**
  * Converts an incoming HttpRequest to an Operation.
  */
-export type RequestParser = AsyncHandler<HttpRequest, Operation>;
+export abstract class RequestParser extends AsyncHandler<HttpRequest, Operation> {}

src/ldp/operations/OperationHandler.ts

@@ -4,4 +4,4 @@ import { Operation } from './Operation';
 /**
  * Handler for a specific operation type.
  */
-export type OperationHandler = AsyncHandler<Operation>;
+export abstract class OperationHandler extends AsyncHandler<Operation> {}

src/ldp/permissions/PermissionsExtractor.ts

@@ -5,4 +5,4 @@ import { PermissionSet } from './PermissionSet';
 /**
  * Verifies which permissions are requested on a given {@link Operation}.
  */
-export type PermissionsExtractor = AsyncHandler<Operation, PermissionSet>;
+export abstract class PermissionsExtractor extends AsyncHandler<Operation, PermissionSet> {}