Maple Rust style

Use the official opentelemetry + opentelemetry_sdk crates with opentelemetry-otlp (HTTP exporter, not gRPC). Bridge the tracing crate: tracing-opentelemetry turns tracing spans into OTel spans, and opentelemetry-appender-tracing turns info! / error! events into OTLP log records.

Cargo.toml

[dependencies]
opentelemetry = "0.32"
opentelemetry_sdk = { version = "0.32", features = ["trace", "logs", "metrics"] }
opentelemetry-otlp = { version = "0.32", features = ["http-proto", "reqwest-blocking-client", "reqwest-rustls", "trace", "logs", "metrics"] }
opentelemetry-appender-tracing = "0.32"
tracing = "0.1"
tracing-subscriber = { version = "0.3", features = ["env-filter"] }
tracing-opentelemetry = "0.33"

Keep the opentelemetry* crates on one minor version, and pair tracing-opentelemetry with the release built for it (0.33 for 0.32). The builder-default batch processors export from their own thread, so use the blocking reqwest client. The async reqwest-client panics there with "there is no reactor running". reqwest-rustls is required for HTTPS: opentelemetry-otlp builds reqwest without default TLS.