docker-compose: db: Set default charset and collation

Signed-off-by: Vasilis Tsiligiannis <acinonyx@openwrt.gr>

docker-compose.yml

@@ -7,6 +7,7 @@ services:
       MYSQL_USER: 'satnogsdb'
       MYSQL_PASSWORD: 'satnogsdb'
       MYSQL_ROOT_PASSWORD: 'toor'
+    command: ['--character-set-server=utf8mb4', '--collation-server=utf8mb4_unicode_ci']
     volumes:
       - type: 'volume'
         source: 'db'