1318: Setup backend test database

[seluianova]

Short description

To add integration tests for the backend (#1532), we need to setup a database. In my opinion, using test containers library is the most convenient way to implement that.

Proposed changes

Add IntegrationTest base class, where database setup is performed. To add new tests that require a database, new test classes must extend the IntegrationTest class.

Side effects

Would be nice to check if everything works on different OS. I have only tested it on Ubuntu 22.04.4 LTS.

Resolved issues

Fixes: #1318