Initial commit

CalDAV and CardDAV checkers sharing a single Go module. Discovery follows
RFC 6764 (/.well-known + SRV/TXT), authenticated probes cover principal,
home-set, collections and a minimal REPORT query on top of go-webdav.
Common shape in internal/dav/; CalDAV adds a scheduling rule.

Surfaces its context URL (and each secure-SRV target) as TLS endpoints via
the EndpointDiscoverer interface, so the dedicated TLS checker can pick
them up without re-parsing observations.

HTML report foregrounds common misconfigs (well-known returning 200,
missing SRV, plaintext-only SRV, missing DAV capability, skipped auth
phase) as action-item callouts before the full phase breakdown.

caldav/definition.go

@@ -0,0 +1,50 @@
+package caldav
+
+import (
+	"time"
+
+	"git.happydns.org/checker-dav/internal/dav"
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+// Version is the checker version reported in CheckerDefinition.Version.
+// Overridden at link time by the standalone binary via -ldflags.
+var Version = "built-in"
+
+// Definition returns the CheckerDefinition for the CalDAV checker.
+func Definition() *sdk.CheckerDefinition {
+	return &sdk.CheckerDefinition{
+		ID:      "caldav",
+		Name:    "CalDAV server",
+		Version: Version,
+		Availability: sdk.CheckerAvailability{
+			// The probe itself only needs a domain name (discovery runs on
+			// the whole domain via /.well-known + SRV), so the checker is
+			// always offered at domain scope.
+			ApplyToDomain: true,
+
+			// Also offered at service scope so alerts — including the TLS
+			// alerts derived from the endpoints we publish — surface on a
+			// dedicated "CalDAV" service page rather than on the domain
+			// page. The abstract.CalDAV service type does not exist in the
+			// happyDomain service catalog yet; until it does, this has no
+			// visible effect, but makes the intent explicit.
+			ApplyToService:  true,
+			LimitToServices: []string{"abstract.CalDAV"},
+		},
+		ObservationKeys: []sdk.ObservationKey{ObservationKey},
+		Options: sdk.CheckerOptionsDocumentation{
+			UserOpts:   dav.UserOptions(),
+			DomainOpts: dav.DomainOptions(),
+			RunOpts:    dav.RunOptions(),
+		},
+		Rules:      dav.Rules(dav.KindCalDAV, ObservationKey),
+		Aggregator: dav.WorstStatus{},
+		Interval: &sdk.CheckIntervalSpec{
+			Min:     1 * time.Minute,
+			Max:     1 * time.Hour,
+			Default: 15 * time.Minute,
+		},
+		HasHTMLReport: true,
+	}
+}