feat: add martin-tracing-utils for configuring tracing (1/3)

[CommanderStorm]

This is the first PR to break out of #1720 to make it reviewable.

The purpose is mainly to see if the added utilities are

• read & undaerstandable
• not magic for others and
• not too verbose
• and the name martin-tracing-utils okay.

Current usage of this code would be

// since logging is not yet available, we have to manually check the locations
let log_filter = LogLevel::from_argument("--log-level")
    .or_in_config_file("--config", "log_level")
    .or_env_var("MARTIN_LOG_FORMAT")
    .lossy_parse_to_filter_with_default("martin=info");
let log_format = LogFormat::from_argument("--log-level")
    .or_in_config_file("--config", "log_format")
    .or_env_var("RUST_LOG")
    .or_default(LogFormatOptions::Compact);
MartinObservability::from((log_filter, log_format))
    .with_initialised_log_tracing()
    .set_global_subscriber();

[Copilot]

Pull Request Overview

This PR introduces the new martin-tracing-utils library to configure tracing for the Martin tileserver. Key changes include:

• Implementation of utilities to initialize and set a global tracing subscriber.
• The addition of CLI, environment variable, and configuration file support for log directives and log format options.
• Updates to workspace configuration and dependencies to integrate the new module.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

File	Description
martin-tracing-utils/src/lib.rs	Implements observability and logging format utilities with tracing integration.
martin-tracing-utils/README.md	Provides documentation for the new tracing utility library.
martin-tracing-utils/Cargo.toml	Defines package metadata and dependencies for the new module.
Cargo.toml	Updates workspace members and adds necessary tracing dependencies.

Comments suppressed due to low confidence (3)

martin-tracing-utils/src/lib.rs:51

• Consider rephrasing the error message in set_global_subscriber for improved clarity, for example: 'Failed to set global subscriber: global subscriber has already been set.'

.expect("since martin has not set the global_default, no global default is set");

martin-tracing-utils/src/lib.rs:115

• [nitpick] Consider using structured logging or a more user-friendly error reporting mechanism instead of eprintln!, and clearly list the accepted log format values.

eprintln!("Ignoring specified cli argument {argument} {v} as it is not a valid log format. Can be one of full, compact, bare, pretty, json");

martin-tracing-utils/src/lib.rs:150

• [nitpick] Consider using a structured logging approach here as well to report invalid log format values from the environment variable, and ensure the message clearly outlines the correct options.

eprintln!("Ignoring specified environment variable {key}={v} as it is not a valid log format. Can be one of full, compact, bare, pretty, json");

[Copilot]

Pull Request Overview

This PR introduces a new utility library, martin-tracing-utils, to configure and initialize tracing for the Martin tile server. Key changes include the implementation of log format and log level extraction from CLI arguments, config file, and environment variables; setting up the global tracing subscriber; and associated tests and documentation updates.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

File	Description
martin-tracing-utils/src/lib.rs	New tracing utilities implementation including log format and level APIs
martin-tracing-utils/README.md	Documentation for the new library with badges and basic usage instructions
martin-tracing-utils/Cargo.toml	Package metadata and dependency setup for the tracing utilities
Cargo.toml	Added the new martin-tracing-utils member to the workspace and dependency updates

Comments suppressed due to low confidence (2)

martin-tracing-utils/src/lib.rs:239

• The variable name 'traversion' appears to be a misspelling; consider renaming it to 'traversal' or another more descriptive name for clarity.

for traversion in key_parts {

martin-tracing-utils/README.md:3

• The documentation badge references 'martin-observability-utils' while the package is named 'martin-tracing-utils'; consider updating the badge link to ensure consistency.

[![docs.rs docs](https://docs.rs/martin-observability-utils/badge.svg)](https://docs.rs/martin-observability-utils)