ConstCaddyDurationSchema.parse("30s"); // OK
CaddyDurationSchema.parse("1h30m"); // OK - combined units
CaddyDurationSchema.parse("1.5d"); // OK - decimal
CaddyDurationSchema.parse("1d2h30m"); // OK - multiple units
CaddyDurationSchema.parse("-30s"); // OK - negative
CaddyDurationSchema.parse(5000000000); // OK - nanoseconds integer
Caddy duration schema - accepts integer (nanoseconds) or Go duration string
Based on Go's time.Duration format with Caddy's "d" (day) extension.