Groups

This is or proposal for group management in viade:

Since solid's address books lacks documentation and we really don't know how to use them we have decided to use or own approach.

Currently we follow the following structure, locating the groups inside /viade/groups
```json
{
"@context": {
"@version": 1.1,
"users": {
"@container": "@list",
"@id": "schema:Person"
},
"name": {
"@id": "schema:name",
"@type": "xs:string"
},
"url": {
"@id": "schema:url",
"@type": "xs:string"
},
"schema": "http://schema.org/",
"xsd": "http://www.w3.org/2001/XMLSchema#"
},
"name": "Group name",
"users": [
{
"name": "contactName",
"url": "https://hellothere.inrupt.net/profile/card#me"
},
{
"name": "contactName",
"url": "https://generalkenobi.inrupt.net/profile/card#me"
}
]
}
```

No source file or test is named; start with the issue's JSON example and inspect the existing specification around /viade/groups. Done should be a resolved group-management proposal with the representation and its expected contents clearly documented.

Written by the indexing model from the issue text.