Add postgres to devcontainer / compose

app/config/dev.exs

@@ -4,7 +4,7 @@ import Config
 config :firehose, Firehose.Repo,
   username: "postgres",
   password: "postgres",
-  hostname: "localhost",
+  hostname: System.get_env("DB_HOST") || "localhost",
   database: "firehose_dev",
   stacktrace: true,
   show_sensitive_data_on_connection_error: true,

app/config/test.exs

@@ -8,7 +8,7 @@ import Config
 config :firehose, Firehose.Repo,
   username: "postgres",
   password: "postgres",
-  hostname: "localhost",
+  hostname: System.get_env("DB_HOST") || "localhost",
   database: "firehose_test#{System.get_env("MIX_TEST_PARTITION")}",
   pool: Ecto.Adapters.SQL.Sandbox,
   pool_size: System.schedulers_online() * 2