Support for Views with primary keys specified in configuration

[Aniruddh25]

As mentioned in the RFC: https://github.com/Azure/project-hawaii/blob/main/rfcs/configuration-file.md#database-object-source

Views are supported and when exposing a view it is required to specify which fields will be used as primary keys:

"source": {
    "type": "table",
    "object": "s002.view_todo",
    "key-fields": [ "title", "author" ]
}

This issue is to add support for such views both for GraphQL.

[Aniruddh25]

@gledis69, The support for such views on the REST side is being implemented by @ayush3797 in #378 . Please sync with him to share ideas.