perf!: slot the public objects user code constructs, receives or holds

[Lancetnik]

The 1.0 half of #3201. The first half, #3220, is merged into main.

Important

The branch starts with a merge of main into 1.0.0 (3d9c5cb), because 1.0.0 does not have #3220 or the other 7 commits main got since the last sync. Until main is merged into 1.0.0, the diff shows those commits too. The PR's own changes are the two commits on top:

• 1508ae0 slots the public objects (below);
• 260c962 slots the config dataclasses, now that 1.0 requires Python 3.11+.

Merge conflicts, all resolved to 1.0.0's version: _internal/fastapi/* (the plugin is gone on 1.0), the Redis connection state and producer (#3131 removed the sync cluster proxy and the separate cluster producer; #3220's __slots__ stay on the classes that remain), and requires-python/version in pyproject.toml.

What this slots

144 classes, all of them objects that user code constructs, receives or holds:

• Messages: StreamMessage and all 16 broker message classes.
• Responses and publish commands: Response, PublishCommand, BatchPublishCommand and every broker's response/command.
• Routers: Registrator, BrokerRouter, every <Broker>Router, <Broker>Route and <Broker>Publisher.
• Test clients: TestApp, TestBroker, the six Test<Broker>Broker and their fakes.
• Context: ContextRepo, Context.
• ASGI: request, response, handlers, AsyncAPI route.
• Specification schema: the dataclasses under faststream/specification/schema/ (Tag, Contact, License, ExternalDocs, the bindings), plus Schedule, Channel and ConsumerBuilder.
• Middleware factories: <Broker>TelemetryMiddleware, <Broker>PrometheusMiddleware, AcknowledgementMiddleware. The per-message instances they create are already slotted in perf: make every declared __slots__ take effect in subclasses too #3220.

It also removes the temporary exclude-classes group that #3220 added for these classes.

Changes beyond a __slots__ line:

• StreamMessage.__copy__ copied through self.__dict__. It now walks the class's slots, so a broker's own slots (KafkaMessage.consumer) are copied too, and a slot that was never assigned stays unset on the copy.
• StreamMessage.background is a declared slot. The FastAPI plugin stores its BackgroundTasks there. When it is unset, getattr(msg, "background", None) still returns None.
• StreamMessage declares __weakref__, so a message can still key a WeakKeyDictionary. __copy__ skips it. tests/message/test_message.py::test_message_takes_a_weak_reference fails without it.

Config dataclasses (260c962)

#3220 left the config chain under BrokerConfig, EndpointConfig and SpecificationConfig unslotted. On 3.10, dataclass(slots=True) re-emits every inherited field into the subclass, which doubles the storage instead of saving it. 1.0 requires 3.11+, so the 37 configs now take slots=True, and their exclude-classes entry is removed.

• Below 3.13, a bare super() in a slotted dataclass still points at the class from before the rebuild. The four such calls, in the Kafka (confluent) and MQTT broker configs, now name their class explicitly.
• RabbitConfig is removed. A mixin with its own fields cannot sit next to a slotted base. queue and exchange are now declared on the four Rabbit configs directly.

Breaking change

These objects no longer accept attributes they do not declare:

message.custom = 1         # AttributeError
Response(b"").custom = 1   # AttributeError
vars(message)              # TypeError

The same applies to the config dataclasses, and faststream.rabbit.configs.RabbitConfig no longer exists.

Not affected:

• A user's own subclass of StreamMessage, Response or a middleware keeps a __dict__.
• The application, the broker, subscribers and publishers keep a __dict__ (perf: make every declared __slots__ take effect in subclasses too #3220), so patch.object(...) on them still works. patch.object(broker.config, ...) goes through the unslotted ConfigComposition proxy, as before.
• Weak references to messages.

Memory

Measured the same way as in #3220 (sys.getsizeof of the object plus its __dict__):

class	bytes before	bytes after
KafkaMessage	344	176
KafkaResponse	344	72
KafkaPublishCommand	344	136
KafkaTelemetryMiddleware (factory)	376	64
KafkaPrometheusMiddleware (factory)	384	72
ChannelBinding (spec dataclass)	344	56

Together with #3220, that is roughly 1.0 KB less per consumed message on a plain Kafka broker, and about 1.7 KB less with OpenTelemetry and Prometheus on. About 0.4 KB of that comes from this PR: the message and the publish command.

Checks

On this branch: slotscheck on 3.11, 3.12, 3.13 and 3.14; mypy, pyright, ruff, and both collection gates; and the not slow and not connected suite on 3.11 (3877 passed), 3.12 (3877 passed) and 3.14 (3853 passed). The in-memory suite covers the super() fix on 3.11 and 3.12. Connected suites were not run.