The init_creates_log_directory_and_file test called init() which sets a
global tracing subscriber. When tests run in parallel, other tests may
have already set the subscriber, causing init() to return an error and
the test to fail. Now the test tolerates the 'already set' error while
still asserting the log file is created.
- Add logging::init() with dual output (file + stdout) via tracing-subscriber Layer composition
- Support configurable log level via LoggingConfig.level and JSON/text format via LoggingConfig.format
- Create log file and parent directories when log_file_path is configured
- Add KvVisitor for custom key=value event field formatting
- Add log_request!, log_rate_limit!, log_upstream_error!, log_config_reload! macros
with REQUEST, RATE_LIMIT, UPSTREAM_ERROR, CONFIG_RELOAD prefixes
- Add format_event_fields() for extracting structured fields from tracing events
- Add tracing-subscriber env-filter and json features to Cargo.toml
- Add unit tests for KvVisitor formatting, log macros, and init function
- Apply cargo fmt to existing tls/config.rs tests