Fix migrations and expand CONTRIBUTING.md docs (#661)

CONTRIBUTING.md

@@ -59,6 +59,11 @@ Firezone development requires access to a Postgresql instance. Versions 9.6 or
 higher should work fine. Access can be configured using the [
 .env](#the-env-file) described below.
 
+**Note:** To use the default configuration without specifying the database URL in the `.env` file, you need to configure the `postgres` user with the password `postgres` to do so use the following command:
+```sql
+ALTER USER postgres WITH PASSWORD 'postgres';
+```
+
 ### Pre-commit
 
 We use [pre-commit](https://pre-commit.com) to catch any static analysis issues

apps/fz_http/priv/repo/migrations/20220124162404_add_uuids.exs

@@ -2,6 +2,11 @@ defmodule FzHttp.Repo.Migrations.AddUuids do
   use Ecto.Migration
 
   def change do
+    execute(
+      "CREATE EXTENSION pgcrypto",
+      "DROP EXTENSION pgcrypto"
+    )
+
     execute(
       "ALTER TABLE rules ADD COLUMN uuid uuid DEFAULT gen_random_uuid() NOT NULL",
       "ALTER TABLE rules DROP COLUMN uuid"