[FEATURE]: lakeflow-framework Python package with contrib extras and absolute imports

[rederik76]

Is there an existing issue for this?

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Problem statement

The framework has no formal namespace, no mechanism for shipping optional community-supported integrations, and no publishable distribution format. Specifically:

1. No proper namespace — source files use bare module imports (from constants import ..., import utility) that have no scope, no discoverability, and break static analysis. There is no lakeflow_framework import prefix that identifies the framework as a distinct, versioned library.
2. No contrib story — there is no formal location or support policy for optional, community-maintained integrations. These currently have no home and no dependency boundary from the core.
3. No standard distribution — customers who want to install the framework from PyPI, Artifactory, or UC Volumes as a wheel cannot do so. Flat directory deployment is the only supported model, which limits adoption and integration patterns.

Proposed Solution

Proper namespace and absolute imports (primary)

• Create src/lakeflow_framework/ as the canonical package namespace.
• Convert source files from bare module imports to absolute imports (from lakeflow_framework.constants import FrameworkPaths). This is the definitive change — it gives the framework a real identity as an importable library.
• Compat shims at the old bare import paths kept until v1.0.0 so existing flat-deploy customers are not broken during the transition window.

contrib/ subdirectory (primary)

• Add src/lakeflow_framework/contrib/ with a README documenting the support policy (experimental, community-maintained, semver rules).
• CI: contrib tests run in a separate optional job gated behind the [contrib] extra.

Python packaging (additional win)

• Add pyproject.toml with [project.optional-dependencies]: contrib and all extras.
• Enables pip install lakeflow-framework from PyPI, Artifactory, UC Volumes, or editable install (pip install -e ".[contrib]") for contributors.

Additional Context

No response