db migration

* note existing DATABASE_URL for historical notes

* comment out the *-db service in manifest.yml (it does not yet exist)

* create the new db service: e.g.
  cf create-service rds shared-psql c2-staging-db
  OR
  cf create-service rds medium-psql c2-prod-db

* dump the existing db to a file
  cssh c2-staging
  curl https://s3.amazonaws.com/18f-cf-cli/psql-9.4.4-ubuntu-14.04.tar.gz | tar xvz
  psql/bin/pg_dump $DATABASE_URL | gzip > c2-staging-2016-04-25.sql.gz
  [leave terminal window open for next step]

* fetch the db dump and push it to a new cf-ssh instance
  [different terminal window]
  cffetch c2-staging-ssh c2-staging-2016-04-25.sql.gz
  cf push c2-staging-worker

* load the dump into the new db service
  cssh c2-staging-worker
  curl https://s3.amazonaws.com/18f-cf-cli/psql-9.4.4-ubuntu-14.04.tar.gz | tar xvz
  zcat c2-staging-2016-04-25.sql.gz | psql/bin/psql $DATABASE_URL

* comment in the *-db service in manifest.yml

* unset DATABASE_URL and re-deploy using service
  cf unset-env c2-staging DATABASE_URL
  cf unset-env c2-staging MAINTENANCE_MODE
  cf push c2-staging
  cf push c2-staging-worker

cffetch and cssh scripts are at https://github.com/pkarman/my-toolbox