docs(#14): Add local db and migrations

docs/database-setup.md

@@ -1,6 +1,10 @@
 # Database Setup
 
-Databases are stored in Supabase. The auth table for signing up and logging in users is created automatically when you set up Supabase Auth. To add the tables for recording their active subscriptions and bought products, as well as products and prices, you can use the following SQL script in the Supabase SQL Editor.
+Databases are stored in Supabase. The auth table for signing up and logging in users is created automatically when you set up Supabase Auth.
+
+## Initial Setup
+
+To add the tables for recording their active subscriptions and bought products, as well as products and prices, you can use the following SQL script in the Supabase SQL Editor.
 
 ```sql
 /**
@@ -164,6 +168,8 @@ create publication supabase_realtime
   for table products, prices;
 ```
 
+## Generating Types
+
 To get the types for the tables, you can follow these instructions taken from [here](https://supabase.com/docs/guides/api/rest/generating-types#generating-types-using-supabase-cli):
 
 `npm i supabase@">=1.8.1" --save-dev`
@@ -177,3 +183,49 @@ Replace `$PROJECT_REF` with your project reference:
 
 Replace `types/supabase.d.ts` with whatever file you want your types in:
 `npx supabase gen types typescript --local > types/supabase.d.ts`
+
+## Local DB Development
+
+Ensure you have [Docker](https://docs.docker.com/get-docker/) installed and running.
+
+You can start and stop the local DB environment with:
+
+```bash
+npx supabase start
+
+npx supabase stop
+```
+
+## Migrations
+
+There are two options to create a migration file:
+
+1. [Writing the SQL manually](https://supabase.com/docs/guides/cli/local-development#database-migrations)
+
+   - Create new blank migration file
+
+     `npx supabase migration new <migration_name>`
+
+   - Add the SQL you want to deploy as part of the migration e.g.
+
+     ```sql
+     create table
+     employees (
+     id bigint primary key generated always as identity,
+     name text,
+     email text,
+     created_at timestamptz default now()
+     );
+     ```
+
+   - Reset the DB and apply the latest migrations
+
+     `supabase db reset`
+
+2. [Generate SQL based on differences to the schema](https://supabase.com/docs/guides/cli/local-development#diffing-changes)
+
+   - With the local DB running, enter the studio and make your changes to the schema
+
+   - Generate the migration file containing the SQL with the differences in the schema
+
+     `npx supabase db diff -f <migration_name>`