Update build to JDK 13

[boskoop]

JDK 13 reached General Availability on 17 September 2019. Projects should build against the latest JDK in order to ensure forward compatibility.

[boskoop]

See PR #65

[boskoop]

Spring Framework 5.1 only officially supports JDK 8-12, but it's probably still a good idea to build against the latest JDK.

See: https://github.com/spring-projects/spring-framework/wiki/Spring-Framework-Versions

[boskoop]

Spring Boot 2.1 does not support JDK 13 -> we need to update support to Spring Boot 2.2 first

[svettwer]

Spring Boot 2.1 does not support JDK 13 -> we need to update support to Spring Boot 2.2 first

And to do this, the Citrus core framework requires a Spring update, so that Spring boot 2.2. is supported. As stated here, we'll release a new version of the Citrus framework most likely until the end of the year. I'll try to include the required spring update there.

BR Sven

[bbortt]

this should be possible within citrus/[email protected].

[bbortt]

main branch is buildable from JDK 17 to 21 (remains to be proven).