getUser method
Implementation
UserInfo getUser(String userNumber) {
if (owner.phoneNumber == userNumber) return owner;
return WorkerInfo._(
userNumber,
(_rawData["workers"].toMap()[userNumber].nullOr ??
_rawData["ex-workers"].toMap()[userNumber].nullOr ??
_rawData["buyers"].toMap()[userNumber].nullOr ??
_rawData["ex-buyers"].toMap()[userNumber])
.toMap(),
);
}