Evaluate DB migration restriction when upgrading to AF 3

[kaxil]

As part of #41120 , we pruned the Database migration files. This change means that users will have to upgrade to Airflow 2.10 before they can upgrade to Airflow 3.0. If a user tried to migrate directly from 2.7 to 3.0 -- they might get an Alembic revision error.

We should re-evaluate this before we release Airflow 3.0 and clearly document the expectation so users don't run into troubles when upgrading to 3.0 from lower Airflow versions.

[kaxil]

fyi @ephraimbuddy

[ashb]

they might get an Alembic revision error.

They will get an alembic version error ERROR [alembic.util.messaging] Can't locate revision identified by ...

[vatsrahul1001]

@kaxil @ashb I did not get this when I tried migration. Can we close this?

[kaxil]

That is because #41994 added migrations from 2.7.

So anything after 2.7 works