DATABASE_METADATA.json enhancement

[fab-10]

What do you think about migrating our DATABASE_METADATA.json content to something more talkative?

I mean now we have:
{"version":2}
wouldn't it clearer to have something like:
{"format": "BONSAI", "version": 1}?
Where format field is BONSAI or FOREST and version is the actual iteration of the format.

I am suggesting that, since I need to introduce a new version of the db, to identify the variables storage upgrade, and since it applies to both formats, with the current metadata, I should introduce 3 and 4 respectively from Forest and Bonsai, but I will prefer to have:

• {"format": "FOREST", "version": 2}
• {"format": "BONSAI", "version": 2}

Changing the DATABASE_METADATA.json format is a breaking change so we also need to define a migration strategy, and how to version the DATABASE_METADATA itself.

We can consider the current DATABASE_METADATA format, the v1, and it has 2 fields:

• version
• privacyVersion

we could introduce v2, changing the format of DATABASE_METADATA.json, adding the version of the metadata itself :

{
  "v2": {
    "format": "BONSAI",
    "version": 2
  }
}

[garyschulte]

relates to #6307