feat: add valuable feature support to appender-tracing

Author: steved

.cargo/config.toml

@@ -1,3 +1,7 @@
+[build]
+# https://github.com/open-telemetry/opentelemetry-rust/issues/2819
+rustflags = ["--cfg", "tracing_unstable"]
+
 [resolver]
 # https://doc.rust-lang.org/cargo/reference/config.html#resolverincompatible-rust-versions
 incompatible-rust-versions = "fallback"

Cargo.toml

@@ -96,6 +96,7 @@ rust_2024_compatibility = { level = "warn", priority = -1 }
 edition_2024_expr_fragment_specifier = "allow"
 if_let_rescope = "allow"
 tail_expr_drop_order = "allow"
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(tracing_unstable)"] }
 
 [workspace.lints.clippy]
 all = { level = "warn", priority = 1 }

opentelemetry-appender-log/Cargo.toml

@@ -22,7 +22,7 @@ opentelemetry-semantic-conventions = { workspace = true, optional = true, featur
 
 [features]
 spec_unstable_logs_enabled = ["opentelemetry/spec_unstable_logs_enabled"]
-with-serde = ["log/kv_serde", "serde"]
+with-serde = ["log/kv_serde", "opentelemetry/with-serde", "serde"]
 experimental_metadata_attributes = ["dep:opentelemetry-semantic-conventions"]
 
 [dev-dependencies]