fix (encounter): add guard for create, delete and cancel

pkg/use-case-helper/use-case-helper.go

@@ -150,3 +150,19 @@ func IsDateBeforeNow(t *time.Time) bool {
 	}
 	return t.Before(time.Now())
 }
+
+// Contains reports whether v is present in s.
+func Contains[S ~[]E, E comparable](s S, v E) bool {
+	return index(s, v) >= 0
+}
+
+// Index returns the index of the first occurrence of v in s,
+// or -1 if not present.
+func index[S ~[]E, E comparable](s S, v E) int {
+	for i := range s {
+		if v == s[i] {
+			return i
+		}
+	}
+	return -1
+}