Allow setting postgres credentials via env vars in dev/test

Author: arnodirlam

config/runtime.exs

@@ -0,0 +1,12 @@
+import Config
+
+# Runtime configuration for database
+# This file is evaluated after compilation, making it suitable for
+# reading environment variables that may change between environments
+
+if config_env() != :prod do
+  config :dx, Dx.Test.Repo,
+    hostname: System.get_env("POSTGRES_HOST", "localhost"),
+    username: System.get_env("POSTGRES_USER", "postgres"),
+    password: System.get_env("POSTGRES_PASSWORD", "postgres")
+end