DRY up the EDM connectors

[alexrichey]

I'm needed to add a connector for plan for our Dagster work, but the existing EDM Connectors are in a less than ideal shape. This refactors them, and adds a plan connector, where we'll put recipes when we plan them in Dagster.

[codecov]

Codecov Report

❌ Patch coverage is 89.44724% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.76%. Comparing base (a142742) to head (83c263a).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
dcpy/connectors/edm/connectors.py	89.89%	13 Missing and 6 partials ⚠️
dcpy/models/connectors/edm/publishing.py	77.77%	2 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
dcpy/lifecycle/connector_registry.py	100.00% <100.00%> (ø)
dcpy/models/connectors/edm/publishing.py	93.33% <77.77%> (-3.89%)	⬇️
dcpy/connectors/edm/connectors.py	89.89% <89.89%> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.