As per this post on StackOverflow, starting with MySQL 8.0.4 they have changed the default authentication plugin for MySQL server from mysql_native_password to caching_sha2_password.
You can either force it back to using the older password plugin or try using the newest MySQL connector/J.
My new error is:
“Cannot create PoolableConnectionFactory (The server time zone value ‘Hora estándar romance’ is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.)”
You need to add a serverTimezone property to the connection properties for that MySQL connection - eg: serverTimezone=UTC or serverTimezone=America/Los Angeles. There's a change going into 7.9.11 that will automatically add the gateway's timezone to your connection string if it's not already populated, but until that happens you will need to set it manually.