🔧(database) allow configuring database with environment variables

The "DATABASES" setting expects a dictionary and we would like to
be able to set it via environment variables but they only allow
strings. With the new "formatter" functionality, we can solve this
by passing a json string and parsing it when reading the setting
from the environment variable.

config/cms/docker_run_production.py

@@ -2,6 +2,7 @@
 This is the settings to run the Open edX CMS with Docker the FUN way.
 """
 
+import json
 import os
 import platform
 
@@ -379,6 +380,7 @@
             "PASSWORD": "password",
         }
     },
+    formatter=json.loads,
 )
 
 # Configure the MODULESTORE

config/lms/docker_run_production.py

@@ -593,6 +593,7 @@
             "PASSWORD": "password",
         }
     },
+    formatter=json.loads,
 )
 
 XQUEUE_INTERFACE = config(