Migrates the unit tests assertions using AwesomeAssertions library.

[GillesTourreau]

Because the last version FluentAssertions become commercial (see fluentassertions/fluentassertions#2943). and there is lot of breaking changes, we have to migrates the unit tests to Awesome Assertions.

Also we have to wait the new version RC version of PosInformatique.AwesomeAssertions.Json.

Related to the PosInformatique/PosInformatique.AwesomeAssertions.Json#1 improvement.