This protects all database access using a Postgres advisory lock. This
way we can avoid problems when two instances of Reshape try to change
the same database at the same time.
The builder will help simplify the tests and avoid boilerplate updates
when need fields are added to the create_table migration. We might want
to add builders all migrations later.
This checks for dangling temporary columns, triggers and function which
were used by migrations but should be removed once the migration has
been completed or aborted.
