Mismatch between the datacontract specification and the datacontract cli in relation to primary key fields

[DiegoGCh]

Hi!

In the datacontract-specification main README, the Field Object and its examples use primaryKey to indicate if the field is a primary key.

At first the primary key field was added as a field called primary. This change was introduced in this commit. Since then, on the release v1.1.0 it was later deprecated due to it changing to primaryKey.

Field Object - README.md

primary deprecation - datacontract.schema.json

But in the datacontract-cli repo, the sqlalchemy-converter still expects the primary key as a field named primary.

So when running a migration that uses this sqlachemy-converter with the primary key set as the datacontract-specification repo indicates, it fails.