dashboard, status API and notifications tell apex domains from hostnames (closes #224)

An apex domain's own records are still saved with the hostnames'
records, under the domain's name, so the port and TLS checks find its
addresses. Notifications about them now start `Domain:`, decided by the
configured domains. The dashboard and /api/v1/status, which read only
the saved state, take a hostname entry whose name also has a domain
entry as that domain's own records: the dashboard shows them in a second
table under Domains, the API in the domain's `recordsByNameserver`, and
neither lists or counts them as hostnames. The startup notification
counts domains and hostnames from the configuration. README says which
of a domain's own records are watched and how their changes are
notified.

Model: opus-5-5

internal/handlers/dashboard.go

@@ -43,12 +43,16 @@ func newDashboardTemplate() *template.Template {
 	)
 }
 
-// dashboardData is the data passed to the dashboard template.
+// dashboardData is the data passed to the dashboard template. Hostnames
+// and DomainRecords split the records in Snapshot.Hostnames, which also
+// holds the apex domains' own (see splitHostnames).
 type dashboardData struct {
-	Snapshot    state.Snapshot
-	Alerts      []notify.AlertEntry
-	StateAge    string
-	GeneratedAt string
+	Snapshot      state.Snapshot
+	Hostnames     map[string]*state.HostnameState
+	DomainRecords map[string]*state.HostnameState
+	Alerts        []notify.AlertEntry
+	StateAge      string
+	GeneratedAt   string
 }
 
 // HandleDashboard returns the dashboard page handler.
@@ -61,12 +65,15 @@ func (h *Handlers) HandleDashboard() http.HandlerFunc {
 	) {
 		snap := h.state.GetSnapshot()
 		alerts := h.notifyHistory.Recent()
+		hostnames, domainRecords := splitHostnames(snap)
 
 		data := dashboardData{
-			Snapshot:    snap,
-			Alerts:      alerts,
-			StateAge:    relTime(snap.LastUpdated),
-			GeneratedAt: time.Now().UTC().Format("2006-01-02 15:04:05"),
+			Snapshot:      snap,
+			Hostnames:     hostnames,
+			DomainRecords: domainRecords,
+			Alerts:        alerts,
+			StateAge:      relTime(snap.LastUpdated),
+			GeneratedAt:   time.Now().UTC().Format("2006-01-02 15:04:05"),
 		}
 
 		writer.Header().Set(