DXCDT-363: Add connection data source

[sergiught]

🔧 Changes

Adding support for connection data sources in this PR. They'll be available by quering based on connection_id or name. However it was necessary to include the enabled_clients as a read only value on the connection resource as we're reusing the same logic as the resource. Historically we removed it when we added the auth0_connection_client association to prevent race conditions, but removing it is unnecessary if the value is read only on the resource.

To note that the description of nested schemas on the connection data source is missing due to faulty behavior on the resource to data source transformation. This will be tackled in a follow up PR: #471.

📚 References

• Support Terraform data sources #22

🔬 Testing

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

[willvedd]

Looks great. I agree with the decision to re-introduce enabled_clients as a read-only field for convenience 👍