confgen: support multi-key map

[Kybxd]

Sometimes we want to map multiple different keys to the same value, but we don't want to occupy to many cells. So we expect keys with the same value can be defined in the same cell. For example:

Group1ItemID	Group1ItemWeight	Group2ItemID	Group2ItemWeight	Group3ItemID	Group3ItemWeight
map<uint32, Group>|{multikey:true}	int32	uint32	int32	uint32	int32
Group1’s ItemID	Group1’s ItemWeight	Group2’s ItemID	Group2’s ItemWeight	Group3’s ItemID	Group3’s ItemWeight
101,102,103	100	201,202	200	301	300

This worksheet generates proto:

message ItemConf {
  option (tableau.worksheet) = {name:"ItemConf"};

  map<uint32, Group> group_map = 1 [(tableau.field) = {name:"Group" key:"ItemID" layout:LAYOUT_HORIZONTAL prop:{multikey:true}}];
  message Group {
    uint32 item_id = 1 [(tableau.field) = {name:"ItemID"}];
    int32 item_weight = 2 [(tableau.field) = {name:"ItemWeight"}];
  }
}

And json:

{
    "groupMap": {
        "101": {
            "itemId": 101,
            "itemWeight": 100
        },
        "102": {
            "itemId": 102,
            "itemWeight": 100
        },
        "103": {
            "itemId": 103,
            "itemWeight": 100
        },
        "201": {
            "itemId": 201,
            "itemWeight": 200
        },
        "202": {
            "itemId": 202,
            "itemWeight": 200
        },
        "301": {
            "itemId": 301,
            "itemWeight": 300
        }
    }
}

[wenchy]

The multikey-map concept is confused. By default, keys are guaranteed to be unique.

1. Multi same keys to different values

• C++ std::multimap

2. A unique composite key (which contains multiple keys) to a value

A data structure to store values with multiple keys in a map.

• Apache MultiKeyMap

So, we should define a accurate and clear naming but not multikey.