Function saveMatch

saveMatch(matchId: string, ratingDelta: number): Promise<string>
Permanently saves a match in the ended match repository.

Note: considering the current implementation of the two repositories, the ID does not change.
Parameters
- matchId: string
  the ID of the match to be saved permanently.
- ratingDelta: number
  the absolute value of the rating score exchanged between players.
Returns Promise<string>
the new ID of the permanently saved match.
- Defined in src/services/match.ts:100