build(mysql): update MySQL version to 8

- Update MySQL image from 5.7 to 8 in GitHub Actions workflow
- Update MySQL image from 5.7 to 8 in Docker Compose file

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     services:
       mysql:
-        image: 'mysql:5.7'
+        image: 'mysql:8'
         env:
           MYSQL_ALLOW_EMPTY_PASSWORD: 1
         volumes:

helper/compose.store.yml

@@ -1,7 +1,7 @@
 version: '3.3'
 services:
   mysql:
-    image: 'mysql:5.7'
+    image: 'mysql:8'
     volumes:
       - /etc/localtime:/etc/localtime:ro
     environment: