Cannot delete an API key generated through OAuth

See: https://rollbar.com/carto/CartoDB/items/37066/

Context

When granting access to other artifacts (a sequence, a view, etc.) to the db role associated to an OAuth generated API key, the role is not dropped.

Steps to Reproduce

Please break down here below all the needed steps to reproduce the issue

1. Authorize a user

https://reveal-user1.carto.com/oauth2/authorize?client_id=8vA48VW9UwMr&response_type=token&state=9808598598718741&redirect_uri=https://localhost:8080/oauth&scope=dataservices:routing

1. Use the access token returned in the previous step to get the session role (in the example below access_token=PJd8M69xWmyoV3P7OnqR3w)

curl -X POST \
  'https://reveal-user1.carto.com/api/v2/sql?api_key=PJd8M69xWmyoV3P7OnqR3w' \
  -H 'Content-Type: application/json' \
  -d '{
    "q": "SELECT session_user"
}'

output: carto_role_c29a4102-e799-426b-80b3-dd851923f1be

1. GRANT SELECT to a table of another user in the same org:

curl -X POST \
  'https://reveal-admin.carto.com/api/v2/sql?api_key=PJd8M69xWmyoV3P7OnqR3w' \
  -H 'Content-Type: application/json' \
  -d '{
    "q": "GRANT SELECT ON \"reveal-admin\".projects TO \"carto_role_c29a4102-e799-426b-80b3-dd851923f1be\""
}'

1. Once the key is expired (and destroyed) the rollbar notification pops up

Current Result

See: https://rollbar.com/carto/CartoDB/items/37066/

Expected result

The role is dropped as expected and the key destroyed.

Additional info

Rollbar issue fixed manually from the rails console:

oat.api_key.send(:db_run, "DROP OWNED BY #{oat.api_key.db_role}"); oat.destroy

We could just include the fix here

summoning @javitonino for triage, feel free to assign it to me 😃

[oleurud]

🚀

[oleurud]

Useful and related documentation: https://www.postgresql.org/docs/10/static/role-removal.html