Find new FlightSQL / ADBC connector for Superset (SQLAlchemy)

[sergiimk]

We currently advise using flightsql-dbapi package to connect from Superset to Kamu Node, which provides a basic SQLAlchemy dialect wrapper on top of FlightSQL.

This package is deprecated and hasn't been updated in over a year, and is now failing to work with Utf8View types. We need to find a replacement.

Prior work:

• adbc-driver-flightsql/ - a maintained ADBC driver that supports Python DBAPI2, but does not provide SQLAlchemy driver
• superset-sqlalchemy-gizmosql-adbc-dialect
• michalc/pgarrow

As a short-term solution a special config option was deployed in #278 to provide compatibility with older clients (should be removed after we find a better solution):

engine:
  datafusionEmbedded:
    useLegacyArrowBufferEncoding: true