subscriber: prepare to release v0.3.0 (#1677)

# 0.3.0 (Oct 22, 2021)

This is a breaking release of `tracing-subscriber`. The primary breaking
change in this release is the removal of the dependency on the [`chrono`
crate], due to [RUSTSEC-2020-0159]. To replace `chrono`, support is
added for formatting timestamps using the [`time` crate] instead.

In addition, this release includes a number of other breaking API
changes, such as adding (limited) support for `#![no_std]` targets,
removing previously deprecated APIs, and more.

### Breaking Changes

- Removed APIs deprecated in the v0.2.x release series.
- Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674])
- Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> +
  ...>` ([#1649])
- Replaced the [`chrono` crate] with the [`time` crate] for timestamp
  formatting, to resolve [RUSTSEC-2020-0159] ([#1646])
- Removed `json` and `env-filter` from default features. They must now
  be enabled explictly ([#1647])
- Changed `FormatEvent::format_event` and `FormatFields::format_fields`
  trait methods to take a `Writer` type, rather than a `&mut dyn
  fmt::Write` trait object ([#1661])
- Changed the signature of the `MakeWriter` trait by adding a lifetime
  parameter ([#781])
  ### Changed

- **layer**: Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674])
- **fmt**: Changed `FormatEvent::format_event` and
  `FormatFields::format_fields` trait methods to take a `Writer` type,
  rather than a `&mut dyn fmt::Write` trait object ([#1661])
- **json**, **env-filter**: `json` and `env-filter` feature flags are no
  longer enabled by default ([#1647])
  ### Removed

- Removed deprecated `CurrentSpan` type ([#1320])
- **registry**: Removed deprecated `SpanRef::parents` iterator, replaced
  by `SpanRef::scope` in [#1431] ([#1648)])
- **layer**: Removed deprecated `Context::scope` iterator, replaced by
  `Context::span_scope` and `Context::event_scope` in [#1431] and
  [#1434] ([#1648)])
- **layer**: Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn
  Layer<S> + ...>`. These interfere with per-layer filtering. ([#1649])
- **fmt**: Removed deprecated `LayerBuilder` type ([#1673])
- **fmt**: Removed `fmt::Layer::on_event` (renamed to
  `fmt::Layer::fmt_event`) ([#1673])
- **fmt**, **chrono**: Removed the `chrono` feature flag and APIs for
  using the [`chrono` crate] for timestamp formatting ([#1646])
  ### Added

- **fmt**, **time**: `LocalTime` and `UtcTime` types for formatting
  timestamps using the [`time` crate] ([#1646])
- **fmt**: Added a lifetime parameter to the `MakeWriter` trait,
  allowing it to return a borrowed writer. This enables implementations
  of `MakeWriter` for types such as `Mutex<T: io::Write>` and
  `std::fs::File`. ([#781])
- **env-filter**: Documentation improvements ([#1637])
- Support for some APIs on `#![no_std]` targets, by disabling the `std`
  feature flag ([#1660])

Thanks to @Folyd and @nmathewson for contributing to this release!

[#1320]: tokio-rs/tracing#1320
[#1673]: tokio-rs/tracing#1673
[#1674]: tokio-rs/tracing#1674
[#1646]: tokio-rs/tracing#1646
[#1647]: tokio-rs/tracing#1647
[#1648]: tokio-rs/tracing#1648
[#1649]: tokio-rs/tracing#1649
[#1660]: tokio-rs/tracing#1660
[#1661]: tokio-rs/tracing#1661
[#1431]: tokio-rs/tracing#1431
[#1434]: tokio-rs/tracing#1434
[#781]: tokio-rs/tracing#781

[`chrono` crate]: https://crates.io/crates/chrono
[`time` crate]: https://crates.io/crates/time
[RUSTSEC-2020-0159]: https://rustsec.org/advisories/RUSTSEC-2020-0159.html

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

tracing-opentelemetry/Cargo.toml

@@ -25,7 +25,7 @@ default = ["tracing-log"]
 opentelemetry = { version = "0.16", default-features = false, features = ["trace"] }
 tracing = { path = "../tracing", version = "0.1", default-features = false, features = ["std"] }
 tracing-core = { path = "../tracing-core", version = "0.1" }
-tracing-subscriber = { path = "../tracing-subscriber", version = "0.2", default-features = false, features = ["registry", "std"] }
+tracing-subscriber = { path = "../tracing-subscriber", version = "0.3", default-features = false, features = ["registry", "std"] }
 tracing-log = { path = "../tracing-log", version = "0.1", default-features = false, optional = true }
 
 [dev-dependencies]