Read 'comment' layer's field property

[wlorenzetti]

Checklist

• [X] I've searched through the current issues to make sure this feature hasn't been requested already.

Motivation

Read the 'comment' property of a layer's fiend and add as 'help' property to vector /api/config REST API.

Suggested solution

Add property help to /api/config vector REST API:

I.e.:

...
},
            {
                "name": "scalerank",
                "type": "float",
                "label": "scalerank",
                "editable": true,
                "validate": {},
                "pk": false,
                "default": "",
                "input": {
                    "type": "float",
                    "options": {}
                },
                "help": "Rank of extention"
            },
{
...

Alternatives considered

No response