Reactive corrections Release

Added Reactive corrections for PersonHandler.save() and corresponding tests.

Stable version with working R2BC

Spring Framework Version = '5.2.3.RELEASE'
Spring Boot Version = '2.2.4.RELEASE'
SpringJpa Version = '2.2.4.RELEASE'
Spring Security Version = '5.2.1.RELEASE'
Spring Cloud Version = '2.2.1.RELEASE'
Spring Cloud Release Train Version = 'Hoxton.SR1'
Spring Boot R2dbc Version = '0.1.0.M3'

R2dbc H2 Version = '0.8.2.RELEASE'
Junit 5 Version = '5.6.0'

Also the project now works with Java 13.