Give each event its own page and show bodies the same everywhere (closes #369)

Each row of the recent events on the webhook page links to the
event's own page, /hook/{id}/events/{eventID}, and expands to show its
body; only the newest starts expanded. The event's page shows its
details, its whole body and every delivery with its attempts.

One renderer, newBodyView with templates/event_body.html, shows a body
in all three places: whole up to 32 KiB, cut there in the lists with a
link to the event's page, JSON pretty-printed, a body of more than 200
lines or 32 KiB in a scrolling box, and a body that is not text left
out beside its download link. A resubmitted copy links to its
original's page.

Model: opus-5-5

internal/handlers/event_detail.go

@@ -0,0 +1,74 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// HandleEventDetail shows one event on its own page: its details,
+// its whole body and every delivery of it. The page reads the
+// event's body whole, which the receiver caps at 1 MB.
+func (h *Handlers) HandleEventDetail() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		webhook, ok := h.ownedWebhook(w, r)
+		if !ok {
+			return
+		}
+
+		if !h.dbMgr.DBExists(webhook.ID) {
+			h.renderError(w, r, http.StatusNotFound)
+
+			return
+		}
+
+		webhookDB, err := h.dbMgr.GetDB(webhook.ID)
+		if err != nil {
+			h.serverError(w, r, "failed to get webhook database", err)
+
+			return
+		}
+
+		var rows []eventLogRow
+
+		err = webhookDB.Model(&database.Event{}).
+			Select(eventColumns).
+			Where(
+				"id = ? AND webhook_id = ?",
+				chi.URLParam(r, "eventID"), webhook.ID,
+			).
+			Limit(1).
+			Find(&rows).Error
+		if err != nil {
+			h.serverError(w, r, "failed to load event", err)
+
+			return
+		}
+
+		if len(rows) == 0 {
+			h.renderError(w, r, http.StatusNotFound)
+
+			return
+		}
+
+		targets, err := h.loadTargetMap(webhook.ID)
+		if err != nil {
+			h.serverError(w, r, "failed to load targets", err)
+
+			return
+		}
+
+		views, ok := h.eventLogViews(
+			w, r, webhookDB, webhook.ID, rows, targets,
+		)
+		if !ok {
+			return
+		}
+
+		h.renderTemplate(w, r, "event_detail.html", map[string]any{
+			tmplKeyWebhook: &webhook,
+			"Event":        views[0],
+		})
+	}
+}