Configure a local only datastore

[ghost]

Is your feature request related to a problem? Please describe.
I would like to use datastore to store my local application's state as well as sync with my GraphQL backend. It would be great to be able to set a directive that specifies the datastore should be used only locally.

Describe the solution you'd like
It would be great to be able to set a directive that specifies whether the datastore is saved locally only or whether it is synced in the backend.

type Company @LocalModel
@key(fields: ["tenant", "createdAt"])
{
    tenant: String!
    createdAt: String!
    name: String!
    sector: String
}

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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