Structured logging, executed

1. static String format(java.util.Map<String, String> fields) — return a deterministic line: keys SORTED alphabetically, each as key=value, joined by a single space. Empty map → empty string. 2. static java.util.Map<String, String> parse(String line) — the inverse: split on single spaces, split each token on the FIRST '=', build the map. 3. static List<String> levelOf(List<String> lines) — extract the value of "level" from each line via parse(). 4. static List<String> actionFor(String level) — the level contract as data: "ERROR"→["page"], "WARN"→["watch"], "INFO"→["ignore"], unknown→["investigate"].

Difficulty: advanced