Spring Security Expose JDBC default user schema DDL location as public constant

The default JDBC user schema is exposed as a classpath resource named org/springframework/security/core/userdetails/jdbc/users.ddl.

We should add a public constant with that classpath location so that users don't need to know the full path.

Comment From: eleftherias

Closed via c6b185465dcb28eaf55dc1b0ee8b42877328bf2c