Add migrations to make DB datetimes tz aware

[Robin5605]

Our models expect the datetimes to be timezone aware, however the database itself has timezone unaware datetimes. This should reconcile that by adding a migration to make the database timezones to be datetime aware.

[jonathan-d-zhang]

up migration

INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Generating static SQL
INFO  [alembic.runtime.migration] Will assume transactional DDL.
BEGIN;

INFO  [alembic.runtime.migration] Running upgrade 6991bcb18f89 -> 56627251b8c0, make datetimes tz aware
-- Running upgrade 6991bcb18f89 -> 56627251b8c0
ALTER TABLE scans
ALTER COLUMN queued_at TYPE TIMESTAMP WITH TIME ZONE USING queued_at AT TIME ZONE 'UTC',
ALTER COLUMN pending_at TYPE TIMESTAMP WITH TIME ZONE USING pending_at AT TIME ZONE 'UTC',
ALTER COLUMN finished_at TYPE TIMESTAMP WITH TIME ZONE USING finished_at AT TIME ZONE 'UTC',
ALTER COLUMN reported_at TYPE TIMESTAMP WITH TIME ZONE USING reported_at AT TIME ZONE 'UTC';;
ANALYZE scans;;
UPDATE alembic_version SET version_num='56627251b8c0' WHERE alembic_version.version_num = '6991bcb18f89';
COMMIT;

down migration:

INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Generating static SQL
INFO  [alembic.runtime.migration] Will assume transactional DDL.
BEGIN;

INFO  [alembic.runtime.migration] Running downgrade 56627251b8c0 -> 6991bcb18f89, make datetimes tz aware
-- Running downgrade 56627251b8c0 -> 6991bcb18f89
ALTER TABLE scans
ALTER COLUMN reported_at TYPE TIMESTAMP WITHOUT TIME ZONE,
ALTER COLUMN finished_at TYPE TIMESTAMP WITHOUT TIME ZONE,
ALTER COLUMN pending_at TYPE TIMESTAMP WITHOUT TIME ZONE,
ALTER COLUMN queued_at TYPE TIMESTAMP WITHOUT TIME ZONE;;
ANALYZE scans;;
UPDATE alembic_version SET version_num='6991bcb18f89' WHERE alembic_version.version_num = '56627251b8c0';
COMMIT;