This PR fixes 2 issues present when generating an application with MS SqlServer as test database.

1. public class defined inside MsSqlTestContainer.java differs from its filename (resulting in compile errors)
2. MSSQLServerContainer provided by org.testcontainers does not support withDatabaseName() method (resulting in a UnsupportedOperationException during tests runtime)

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• All continuous integration tests are green
• Tests are added where necessary
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