Function resolve 

pub(super) async fn resolve<T: TransactedSyncV4Queries>(
    transaction: &mut T,
    key: ConnectionKey,
    pos: Option<String>,
) -> Result<ResolvedConnection, SyncV4Error>

Resolves a connection from its (user ID, device ID, connection ID) triplet.

This will also insert/delete a connection when needed.

Errors

• SyncV4Error::SyncTokenParseError: Well, obviously, if we failed to parse the request’s token.
• SyncV4Error::InternalServerError: If anything went wrong on our side (most likely while communicating with the database).
• SyncV4Error::UnknownPos: If the request contains a pos token but we did not find any connection stored for the given triplet, or that position is not found in the connection.
• SyncV4Error::PosFromFuture: If the given pos contains a token that is past the server’s current token (see sync_token::get_current_token).