TODOs for this chapter as there are some things I haven't cleaned up yet.

- Fix validation error message that results when submitting an empty ticket from the portal. Right now it says

Failed to convert property value of type java.lang.String to required type org.springframework.hateoas.Link for property
category; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type
java.lang.String to type @javax.validation.constraints.NotNull org.springframework.hateoas.Link for value '; nested
exception is java.lang.IllegalArgumentException: Href must not be null or empty!

* Add findByKey() to the TicketCategoryRepository, going all the way back to recipe 13.1

* Update 13.3 to get rid of the REST calls that the help desk app makes to the portal. Get rid of both the client and
  the service. This also means getting rid of the Spring HATEOAS resources and replacing them with our CDM DTOs. Remove
  the dependencies from the POM, remove the REST annotations from the Spring Data JPA repos, etc.

* In recipe 13.3, replace the hardcoded Rabbit guest/guest credentials with property placeholder creds. Do this for
  both help desk and portal. Merge this forward.
