feat: introduce seatbelt crate

[martintmk]

Introduces seatbelt, a production-ready resilience middleware crate providing:

• Retry: Automatic retries with configurable backoff (constant, linear, exponential) and jitter
• Timeout: Cancellation of long-running operations with per-request overrides
• Circuit Breaker: Prevents cascading failures by blocking requests when failure rates exceed thresholds

Key features:

• Runtime-agnostic design (works with any async runtime via tick::Clock)
• Type-state pattern enforces correct configuration at compile time
• OpenTelemetry metrics and structured logging support
• Composable layers compatible with tower/layered middleware stacks

Example:

let clock = Clock::new_tokio();
  let context = ResilienceContext::new(&clock).name("my_service");

  let stack = (
      // Retry: recover from transient failures
      Retry::layer("retry", &context)
          .clone_input()
          .max_retry_attempts(3)
          .backoff(Backoff::Exponential)
          .recovery_with(|output: &Result<String, String>, _| match output {
              Ok(_) => RecoveryInfo::never(),
              Err(_) => RecoveryInfo::retry(),
          }),
      // Circuit breaker: stop calling failing services
      Breaker::layer("circuit", &context)
          .recovery_with(|output: &Result<String, String>, _| match output {
              Ok(_) => RecoveryInfo::never(),
              Err(_) => RecoveryInfo::retry(),
          })
          .rejected_input_error(|_, _| "circuit open".to_string()),
      // Timeout: bound operation duration
      Timeout::layer("timeout", &context)
          .timeout(Duration::from_secs(5))
          .timeout_output(|_| Err("timeout".to_string())),
      Execute::new(call_external_service),
  );

  let service = stack.into_service();
  let result = service.execute("request".to_string()).await;

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.0%. Comparing base (fa3d815) to head (f989b49).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##             main     #203     +/-   ##
=========================================
  Coverage   100.0%   100.0%             
=========================================
  Files         105      135     +30     
  Lines        6783     8161   +1378     
=========================================
+ Hits         6783     8161   +1378     

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[github-actions]

⚠️ Breaking Changes Detected

error: failed to retrieve local crate data from git revision

Caused by:
    0: failed to retrieve manifest file from git revision source
    1: possibly due to errors: [
         failed when reading /home/runner/work/oxidizer/oxidizer/target/semver-checks/git-origin_main/1101a22c99c13f720565990cb0cdf10dabd2cf12/scripts/crate-template/Cargo.toml: TOML parse error at line 9, column 26
         |
       9 | keywords = ["oxidizer", {{CRATE_KEYWORDS}}]
         |                          ^
       missing key for inline table element, expected key
       : TOML parse error at line 9, column 26
         |
       9 | keywords = ["oxidizer", {{CRATE_KEYWORDS}}]
         |                          ^
       missing key for inline table element, expected key
       ,
         failed to parse /home/runner/work/oxidizer/oxidizer/target/semver-checks/git-origin_main/1101a22c99c13f720565990cb0cdf10dabd2cf12/Cargo.toml: no `package` table,
       ]
    2: package `seatbelt` not found in /home/runner/work/oxidizer/oxidizer/target/semver-checks/git-origin_main/1101a22c99c13f720565990cb0cdf10dabd2cf12

Stack backtrace:
   0: anyhow::error::<impl anyhow::Error>::msg
   1: cargo_semver_checks::rustdoc_gen::RustdocFromProjectRoot::get_crate_source
   2: cargo_semver_checks::rustdoc_gen::StatefulRustdocGenerator<cargo_semver_checks::rustdoc_gen::CoupledState>::prepare_generator
   3: cargo_semver_checks::Check::check_release::{{closure}}
   4: cargo_semver_checks::Check::check_release
   5: cargo_semver_checks::exit_on_error
   6: cargo_semver_checks::main
   7: std::sys::backtrace::__rust_begin_short_backtrace
   8: main
   9: <unknown>
  10: __libc_start_main
  11: _start

If the breaking changes are intentional then everything is fine - this message is merely informative.

Remember to apply a version number bump with the correct severity when publishing a version with breaking changes (1.x.x -> 2.x.x or 0.1.x -> 0.2.x).

[geeknoid]

Check out the "Alerts" tab in GitHub. It mentions public APIs which are referencing items whose docs are being hidden, which seems like an anti-pattern. I don't know why these items are showing up in that tab instead of breaking the build...

[geeknoid]

Uh ho, the CLA check is failing. You might need to close and reopen the PR...