feat: index ownership changes, bump min go version

internal/handler/ownership.go

@@ -0,0 +1,11 @@
+package handler
+
+import (
+	"context"
+
+	"github.com/grassrootseconomics/eth-tracker/pkg/event"
+)
+
+func (h *Handler) IndexOwnershipChange(ctx context.Context, event event.Event) error {
+	return h.store.InsertOwnershipChange(ctx, event)
+}