Persist twitter alerts in database

[amasnik]

Persist alerst in mysql database

Switch in-memory implementation with real mysql database.

Acceptance Criteria:

• Database model for alerts is defined
• Alerts are persisted in database
• Integration test for fetching alerts from twitter and persisting them in DB

** Tests should be written with testcontainers implementation (https://www.testcontainers.org/) This will help to run them in CI github actions.