What should the value of beckn key in context.jsonld be?

In the existing schema.beckn.io schema objects, the context.jsonld has various values for the "beckn" key. Some of them are below:

```
"beckn": "https://schema.beckn.io/LinkedData/v2.1/context.jsonld"
"beckn": "https://schema.beckn.io/linked-data/latest-context.jsonld"
"beckn": "https://schema.beckn.io/mobility/v2.0/"
"beckn": "https://schema.beckn.io/core/v2.0/"
"beckn": "https://schema.beckn.io/"
```

As you can see, it is not consistent. Also though they are shown as urls, most of them do not resolve. Some of them are not valid prefixes either.

We need to have a consistent approach to what to put as the base-iri.