Add missing javassist dependency

[cescoffier]

Thymeleaf template engine requires Javassist.

We need to add this dependency again:

<dependency>
    <groupId>org.javassist</groupId>
    <artifactId>javassist</artifactId>
    <version>3.18.2-GA</version>
</dependency>

This dependency needs to be added into the web stack. We need an automated example to check the fix.

[purplefox]

We need to be very careful about that as Netty can behave differently if Javassist is on the classpath and requires a specific version.

[cescoffier]

Yes,

Previously we depended on 3.18.1-GA. We removed it when we dropped the mysql/posgres client. The safest would be to reuse the same version.