switch to jndi datasource

src/main/resources/application.properties

@@ -1,6 +1,4 @@
-spring.datasource.url=jdbc:mysql://localhost:3306/clubhelper?useUnicode=yes;characterEncoding=utf8
-spring.datasource.username=markus
-spring.datasource.password=0773
+spring.datasource.jndi-name=jdbc/clubhelperbackend
 
 spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL8Dialect
 spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.ImprovedNamingStrategy