Switch from MySQL to SQLite for simpler deployment

config/database.yml

@@ -1,20 +1,16 @@
 default: &default
-  adapter: mysql2
-  encoding: utf8mb4
+  adapter: sqlite3
   pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
-  username: <%= ENV.fetch("DB_USERNAME") { "root" } %>
-  password: <%= ENV.fetch("DB_PASSWORD") { "" } %>
-  host: <%= ENV.fetch("DB_HOST") { "localhost" } %>
-  port: <%= ENV.fetch("DB_PORT") { 3306 } %>
+  timeout: 5000
 
 development:
   <<: *default
-  database: rails_test_development
+  database: db/development.sqlite3
 
 test:
   <<: *default
-  database: rails_test_test
+  database: db/test.sqlite3
 
 production:
   <<: *default
-  database: <%= ENV.fetch("DB_NAME") { "rails_test_production" } %>
+  database: db/production.sqlite3