feat: add TravelContainer class, Firebase dependency and unit tests

[RemIsMyWaifuu]

Basic implementation for the Travel data model as well as related classes. Unit Tests that checks basic requirements, and addition of necessary dependency is added. This is necessary for user stories #8 #14 #10 to have a common base. Details are open to change but the overall structure should stay the same.

Closes #15

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud