GATT server support for Rust

With a whole lot of support to get there:

- Device::add_service(), with some complexity around how to represent the mutable Python `Service` being used under the covers
- AttributePermission, CharacteristicProperty, and other supporting GATT-related stuff
- Ability to handle the different data types used by various Python `Characteristic` subclasses
- Support for running tests in the context of a background `rootcanal` process
- `TryToPy` and `TryFromPy` traits to help make the lifecycle more clear for structs that have a Python equivalent, but are also meaningful standalone
- Add example with a minimal battery service
- Rearrange known service IDs to make it possible to refer to a service UUID in a meaningful way
- Make Address hold its own state to avoid propagating PyResult so much, and adopt the new TryToPy and TryFromPy traits
- `AdvertisingDataValue` trait so users don't have to remember as many ADU encoding details at a call site
- Sprinkle in more wrap_python_async to work on Python 3.8 and 3.9

Author: marshallpierce

bumble/device.py

@@ -44,7 +44,7 @@
 from pyee import EventEmitter
 
 from .colors import color
-from .att import ATT_CID, ATT_DEFAULT_MTU, ATT_PDU
+from .att import ATT_CID, ATT_DEFAULT_MTU, ATT_PDU, Attribute
 from .gatt import Characteristic, Descriptor, Service
 from .hci import (
     HCI_AUTHENTICATED_COMBINATION_KEY_GENERATED_FROM_P_192_TYPE,
@@ -3533,7 +3533,12 @@ def add_default_services(self, generic_access_service=True):
     async def notify_subscriber(self, connection, attribute, value=None, force=False):
         await self.gatt_server.notify_subscriber(connection, attribute, value, force)
 
-    async def notify_subscribers(self, attribute, value=None, force=False):
+    async def notify_subscribers(
+        self,
+        attribute: Attribute,
+        value: Optional[bytes] = None,
+        force: bool = False,
+    ) -> None:
         await self.gatt_server.notify_subscribers(attribute, value, force)
 
     async def indicate_subscriber(self, connection, attribute, value=None, force=False):

bumble/gatt_server.py

@@ -491,7 +491,7 @@ async def notify_subscribers(
         attribute: Attribute,
         value: Optional[bytes] = None,
         force: bool = False,
-    ):
+    ) -> None:
         return await self.notify_or_indicate_subscribers(False, attribute, value, force)
 
     async def indicate_subscribers(