Add tests

[micrusa]

Added e2e tests for utils and unit test for AI.

• Utils: ensures all endpoints work correctly. Tests OAS Spec returns expected result for all possible combinations of specFile / spec configurations

To test it:

• npm run build, to build the test servers
• npm test, to run the test suite

[motero2k]

Utils tests must be written like the other test files. BeforeAll should be called once.

[micrusa]

• Fixed recreating the server for each test by using an unit test instead, which makes more sense for utils
• Added negative tests for edge cases in auth: incorrect payload types, different jwt secrets and expired tokens