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 +1,41 @@
+package caldav
+
+import (
+	"time"
+
+	"git.happydns.org/checker-dav/internal/dav"
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+// Version is overridden at link time by the standalone binary via -ldflags.
+var Version = "built-in"
+
+func (p *caldavProvider) Definition() *sdk.CheckerDefinition {
+	return &sdk.CheckerDefinition{
+		ID:      "caldav",
+		Name:    "CalDAV server",
+		Version: Version,
+		Availability: sdk.CheckerAvailability{
+			ApplyToDomain: true,
+			// Service scope keeps downstream TLS alerts on a dedicated
+			// "CalDAV" page rather than the domain page. abstract.CalDAV
+			// isn't in the catalog yet, so this is a no-op until it is.
+			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,
+	}
+}