Replace YAML-specific functions with generic ones accepting unmarshaler/marshaler
function parameters. This enables future support for JSON and other formats
while maintaining current YAML behavior.
- UnmarshalValidateYAML -> UnmarshalValidate(unmarshalFunc)
- UnmarshalValidateYAMLXSync -> UnmarshalValidateXSync(unmarshalFunc)
- SaveJSON -> SaveFile(marshalFunc)
- LoadJSONIfExist -> LoadFileIfExist(unmarshalFunc)
- Add UnmarshalValidateReader for reader-based decoding
Testing: all 12 staged test files updated to use new API
The icon fetching logic now checks if the target service is healthy before
attempting to fetch icons. If the health monitor reports an unhealthy status,
the function returns HTTP 503 Service Unavailable instead of proceeding.
Additionally, the icon cache lookup now includes infinite retry logic with a
15-second backoff interval, improving resilience during transient service
outages. Previously, failed lookups would not be retried.
The `route` interface was extended with a `HealthMonitor()` method to support
the health check functionality.
