[MCC-1498582] - Create layered design

[slingampalli-mdsol]

[MCC-1498582] - Create layered design

Changes

• Added a transport layer contract (DTOs + abstract Transport) and an Arrow Flight transport implementation with exception translation.
• Added a service layer (DataConnectService + default implementation) to map transport resources into domain models and translate transport errors into public exceptions.
• Updated the public client/models/exceptions surface to align with the new layered architecture.

[Copilot]

Pull request overview

This PR restructures the SDK into clearer layers by introducing a technology-agnostic transport interface (with an Arrow Flight implementation), a service layer that performs domain mapping and error translation, and a thinner DataConnectClient façade as the composition root.

Changes:

• Added a transport layer contract (DTOs + abstract Transport) and an Arrow Flight transport implementation with exception translation.
• Added a service layer (DataConnectService + default implementation) to map transport resources into domain models and translate transport errors into public exceptions.
• Updated the public client/models/exceptions surface to align with the new layered architecture.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
dataconnect/transport/models.py	Adds transport-layer DTOs (ResourceQuery, ResourceInfo, DataRef).
dataconnect/transport/errors.py	Introduces internal transport-only exception hierarchy.
dataconnect/transport/base.py	Defines the technology-agnostic Transport interface.
dataconnect/transport/arrow_flight/transport.py	Implements Transport using pyarrow.flight and translates Flight errors to transport errors.
dataconnect/transport/arrow_flight/init.py	Exposes ArrowFlightTransport.
dataconnect/transport/init.py	Public exports for the transport layer (excluding internal transport errors).
dataconnect/service/mappers.py	Adds mapper(s) from transport ResourceInfo to domain models.
dataconnect/service/default.py	Adds default service implementation with error translation + study retrieval.
dataconnect/service/base.py	Defines the service interface (DataConnectService).
dataconnect/service/init.py	Re-exports service symbols for convenience.
dataconnect/models.py	Updates domain models to UUID-based Study/StudyEnvironment.
dataconnect/exceptions.py	Expands and documents public exception hierarchy; adds ServerError.status_code.
dataconnect/client.py	Refactors client into a thin façade over the service; adds connect() composition root.
dataconnect/init.py	Updates package-level exports to match new public API surface.

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