Upgrade to Spring Boot 2.3.1.RELEASE

Upgrade to Spring Cloud Hoxton.SR5 and Spring Boot 2.2.8.RELEASE

Remove spring-cloud-starter-loadbalancer dependency already included by spring-cloud-starter-netflix-eureka-client

* Add circuit breaker to the getVisitsForPets method

* Use Collections.emptyMap()

* Fallback method with private visibility

* Unit test Hystrix fallback method

* Introduce assertDescriptionEquals method

* VisitsServiceClientTest refactoring

* #72 Upgrade to Spring Cloud Finchley M9

* #72 Upgrade to Spring Boot 2.0.1

* #72 Remove @Deprecated API usage

* #72 Upgrade to Spring Cloud Finchley RC2, Spring Boot 2.0.2, Sleuth 2.0.0.RC2, Zipkin Server 2.8.4

* #72 Registering the index ViewController is no more required

* For logging, implement the toString() method of the Pet entity

* #72 Upgrade to Spring Boot Admin 2.0.0

* #72 Add @NoArgsConstructor required for Jackson deserialization

* #72 Upgrade to Spring Boot 2.0.3

* #72 Upgrade to Spring Cloud Finchley RELEASE

* Change Zipkin local host URL

* #72 changes requested by the @mszarlinski code review

* Upgrade to Spring Cloud Camden.SR5 and Spring Boot 1.5

* #44 Fix maven project versionning