Celery

Changed

- `CeleryBuilder::task_route` now infallible. Error could be raised during the `build` phase instead.
- `Celery::consume_from` will return `Err(CeleryError::NoQueueToConsume)` if the slice of queues is empty.

Changed

- `Celery::consume_from` now takes multiple queues instead of just a single queue.
- Retry ETA method moved from tracer to task so that it can be customized.
- `TaskError` variants restricted to only `ExpectedError`, `UnexpectedError`, and `TimeoutError`. The `Retry` and `ExpirationError` variants moved to a new (non-public) error type: `TracerError`.

Added

- `on_failure` and `on_success` options to `task` attribute macro.

Changed

- Removed `task_id` and `params` arguments to `on_failure` and `on_success` callbacks, since those can be gotten from the request object.

Added

- A `Signature` struct with includes task execution options (previously the fields in `TaskSendOptions`).
- A `bind` argument to the `task` macro. When `bind = true` is given, the task will be run as an instance method.
- A `Request` struct.

Changed

- `protocol::TryIntoMessage` trait renamed to `TryCreateMessage` and the one trait function `try_into_message` renamed to `try_create_message` to better reflect the fact that the trait function does not consume `self`.
- Task parameters are now separated from task struct.
- Task callback methods `on_failure` and `on_success` are now instance methods.
- `Celery::send_task` now takes a `Signature` instead of a `Task`.
- When tasks are defined through the `task` macro by annotating a function, that function needs to be explicitly marked async for the function to use async / await syntax.

Removed

- `TaskContext` struct.
- `TaskSendOptions`.
- `Celery::send_task_with`.

Changed

- Uses of `std::sync::Mutex` and `std::sync::RwLock` changed to their async-aware equivalents from `tokio`.
- The `Celery::register_task` method is now an async function due to the above.
- Fixed bug where tasks with a future ETA were acked before they were due, resulting in such tasks being lost if the worker was shutdown before they were due.

Removed

- The `SyncError` variants have been removed.

Changed

- `Celery::consume_from` now only accepts a single queue (once again) since there was a critical bug when we allowed consuming from multiple queues.