refactor: change methods visibility and rework project structure

[JeremyPansier]

Checklist:

• [x] The code follows our code conventions.
• [x] Important principle changes have been documented in the wiki.
• [x] The new code is covered by unit tests with assertions.
• [x] The behaviour node and UI have been manually tested and is as expected.
• [x] The squash commit message follows our conventions.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
8 Code Smells

60.0% Coverage
0.0% Duplication