Add unit test for sequential POST requests to /set_data with random data validation

[Sophie-Ag00001]

PR Description: Add Unit Test for /set_data API Route

Summary

This PR adds a unit test to src/tests/mod.rs to verify the behavior of the /set_data API route. The test sends 3 sequential POST requests with random data to the same address and ensures the response contains all previously sent data entries. This ensures the API correctly accumulates and returns data across multiple requests.

Context

The /set_data route is expected to store and return all data entries sent to it. This test validates that the API behaves as intended when handling multiple requests with new, random data. The test uses a test-specific database and filter instance to isolate the test environment.

Testing Instructions

1. Run the test suite using cargo test.
2. Verify that the new test test_set_data_multiple_requests passes.
3. Ensure no other tests are affected by these changes.

Known Issues/Limitations

• The test assumes the /set_data route is already implemented and functional.
• The test does not cover edge cases such as invalid data formats or large payloads.