Add additional tests for the server

[manuelwedler]

follow-up of #1429

I found parts of the server for which it would be nice to add additional tests. We generally want to increase our test coverage. The following parts need additional tests (all inside server/src/server folder):

• server.ts: Rate limiting (lines 194 - 234) should be tested
• session.ts: Memory session is not tested
• controllers/verification/session-state/session-state.handlers.ts: In this file, we should test adding remote files (line 35), and the addInputContractEndpoint is completely uncovered.
• services/compiler/lambda and services/compiler/lambda-with-fallback: These are not covered at all.
• services/storageServices/AllianceDatabaseService.ts is not really tested. Generally, we want to have separate tests for the different storage services. It would be nice to add these as part of this issue.