Add a NewProviderPlugin loader alongside the existing checker plugin
loader. The factory returns a ProviderCreatorFunc / ProviderInfos pair,
which is registered through internal/provider.RegisterProvider so plugin
providers appear in the registry like the built-in ones.
Scan -plugins-directory paths at startup, open each .so via plugin.Open,
look up the NewCheckerPlugin symbol from checker-sdk-go, and register the
returned definition and observation provider in the global checker
registries. A pluginLoader indirection keeps the door open for future
plugin kinds.
Add the checker-sdk-go dependency and build the core checker
infrastructure:
- Domain model types: CheckTarget, CheckPlan, Execution,
CheckEvaluation, CheckerDefinition, CheckerOptions,
ObservationSnapshot, and associated interfaces
- Observation collection engine with concurrent per-key gathering
- Checker and observation provider registries (wrapping checker-sdk-go)
- WorstStatusAggregator for combining rule evaluation results
- AutoFill constants for context-driven option resolution
- Config option and CLI flag for max observation concurrency
- Revised error types for the checker domain
Integrates optional bot protection on the registration endpoint (always
required when a provider is configured) and the login endpoint (triggered
after N consecutive failures for the same IP or email address).
Supported providers: hCaptcha, reCAPTCHA v2, Cloudflare Turnstile.
