Adding a check type

Add a new kind of monitor.

A check type is a config struct and a function in crates/checks, plus a form in the frontend. The server and database need no changes.

  1. Write the check. Add a module in crates/checks/src/ with a config struct (Serialize, Deserialize), a validate() method, and an async fn check(...) -> CheckOutcome. Look at tcp.rs for a small example.

  2. Register it in crates/checks/src/lib.rs:

    • add the module and re-export it;
    • add a variant to CheckConfig. Its kebab-case name becomes the type value in JSON;
    • add arms to validate and check;
    • if the config holds secrets, handle them in redact and keep_secrets_from;
    • if the service reports in rather than being checked, update is_passive.

  3. Check the target. The dashboard shows a service's target from the config's url, host or container field. If yours uses another key, add a migration that updates the generated target column.

  4. Add the form. In frontend/src/routes/(dashboard)/services/new/+page.svelte, add the type to serviceTypes, its fields to the form, and its config to buildConfig(). Check services/[id]/+page.svelte shows it correctly.

  5. Test and document it. Add unit tests next to the check, and a page in landing/content/docs/monitors/, linked from the check types table.