Extend Physical identifiers

[entin-hun]

Background:
The current DID specification focuses on providing a decentralized identifier for any subject. However, many applications that utilize DIDs involves physical identification (e.g. location at given time{range}), such as supply chain management, asset tracking, and geospatial services.

Proposal:
I propose extending the DID specification to include fields for GeoJSON, and maybe time(range) and other physical data.
GeoJSON is a widely used format for encoding geographic data structures. Incorporating GeoJSON fields into DIDs will allow for the representation of points, lines, polygons, and other geographical features directly within the DID document.

Specific Changes:

•	Introduce a new geoJson field in the DID document to store geographic data.
•	The geoJson field should accept any valid GeoJSON object, such as Point, LineString, Polygon, etc.
•	Example of how the DID document might look with a GeoJSON field:

{
  "@context": "https://www.w3.org/ns/did/v1",
  "id": "did:example:123456789abcdefghi",
  "geoJson": {
    "type": "Point",
    "coordinates": [125.6, 10.1]
  }
}

Use Cases:

•	Tracking the geographic location of assets in a supply chain.
•	Associating specific DIDs with physical locations, such as landmarks or facilities.
•	Enhancing geospatial services with decentralized identifiers.

Impact:

•	This extension will significantly enhance the utility of DIDs for use cases that require geographic data, promoting broader adoption in sectors like logistics, environmental monitoring, and smart cities.