test(openchallenges): improve organization service model ImageResponse and OrganizationMapper unit test coverage

[mdsage1]

Description

Changes include packages w/a single class.
Sonar unit test coverage has been increased to 12% for model/mapper package. This package has a single class, OrganizationMapper.
Sonar unit test coverage has been increased to 100% for service/model/rest/response package. This package has a single class, ImageResponse.
The OrganizationServiceApplication class in the organization/service package is the only class in that package but the only uncovered code would be categorized as an integration test while the focus here is on unit testing.

A comment was also added to OrganizationServiceApplication for the existing integration test. This confused me and I had to deep dive into what was happening to find out that it was an integration test rather than a unit test.

Related Issue

#2063
#1528
#2348

Changelog

See files Changed section

These changes have not increased the Sonar coverage above the 15%,9.5% according to the Code Quality Dashboard, achieved with the exception unit test PR #2348 but, different components, methods etc., of these packages' classes are being tested by the unit tests added. These tests were written last week and debugged this week. The PR has been released after the approval of the exception unit test PR on 2023-12-04.

Preview

The Sonar coverage increase for model/mapper:

The Sonar coverage increase for service/model/rest/response:

[tschaffter]

Looks good overall! See comments below

[mdsage1]

1. Removed the comment regarding the integration test in service/OrganizationServiceApplicationTests
2. Renamed organizationEntity to entity in model/mapper/OrganizationMapperTest.java
3. Renamed user variable to dTo in service/model/mapper/OrganizationMapperTest.java
4. Changed the variable names that used retrieved to actual throughout model/mapper/OrganizationMapperTest.java

[tschaffter]

1. Removed the comment regarding the integration test in service/OrganizationServiceApplicationTests
   ...

Let's keep the discussion in their respective thread. When you address a comment from a reviewer, you can either close it or comment + close it if you have addressed it. If work is in progress or clarification is needed, keep the comment thread open. Thanks!