Use env variables rather than custom ci scripts

.github/workflows/mysql.yaml

@@ -9,6 +9,14 @@ jobs:
   test:
     runs-on: ubuntu-latest
 
+    env:
+      # Database backend configuration
+      INVENTREE_DB_ENGINE: django.db.backends.mysql
+      INVENTREE_DB_USER: root
+      INVENTREE_DB_PASSWORD: password
+      INVENTREE_DB_HOST: '127.0.0.1'
+      INVENTREE_DB_PORT: 3306
+
     services:
       mysql:
         image: mysql:latest