Module leaderboard 

Leaderboard protocol: submit scores, fetch boards, paginate results.

Speaks JSON over HttpClient (needs the http feature for real network access). The expected server API:

• POST {base}/scores with {"player_id", "name", "score", "metadata", "checksum"?, "replay_id"?}, answered with {"rank", "score"}.
• GET {base}/scores?period=&class=&page=&page_size= answered with either a JSON array of entries or {"entries": [...], "total": N}.
• GET {base}/scores/{player_id} answered with one entry.

An entry is {"rank", "player_id" (or "id"), "name", "score", "metadata"?, "timestamp"?, "replay_url"?}; numbers may also be strings.

Structs

LeaderboardClient

High-level leaderboard API built on top of HttpClient.

LeaderboardFilter

Which part of the board to fetch.

ScoreEntry

One row of a leaderboard.

ScoreSubmission

A score to send to the board.

Enums

LeaderboardEvent

Results from LeaderboardClient::drain_events.