Allow generating migration revisions from docker-compose

@DSASanFrancisco/portal-members

Fixes issues with running migrations locally by mounting the source code but keeping the path the same as the built docker image.

If we don't keep the paths the same, then we have to override the command argument used to run the script locally than we do in the docker container.

@Mbamesb2 I finally figured out this issue. We should now be able to run:

docker-compose run migrate alembic revision --autogenerate -m "my migration"

And this will generate a migration for us.