Suggestion on improving the crosstable API

Right now the crosstable API receives just two users and returns a total number of games and the score for each user.

These are my issues with it:

• the number of games is pointless, as it is the total of the two player scores
• it matters what kind of games they were. It makes no sense to add bullet scores to correspondence or variants scores
• the output of the API contains a lot less information that the graphical component called crosstable, which makes this endpoint feel like something else.
• it's inefficient when having to show crosstables in lists, like in any list of games or the lobby - where a user requested it specifically.

So my recommendation is a second POST endpoint for crosstable which receives a JSON array of tuples of player ids and returns the array of crosstable scores split per game type (blitz, bullet, atomic, etc.)

Start with the documented GET /api/crosstable/{user1}/{user2} endpoint and compare its response with the graphical crosstable component. Clarify the POST request and per-game-type response shape, batching behavior, and completion criteria before identifying the implementation and documentation changes.