api should use the db settings from shared

[nora-shap]

One more task to smooth over the big job of moving a bunch of our models to shared

We learned that that api is still using its own settings for many of the db_settings (look at settings_base), when it should be importing from db_settings in shared.

to fix:

• add from shared.django_apps.db_settings import * to api,
• go over settings_base in api,
• remove any that now live in shared so that api will use the settings from shared.

[thomasrockhu-codecov]

@nora-codecov let's chat about this for next sprint and see what the work involved is