- Add filtering by query, player capacity, spectators capacity, number of players, number of spectators, location name, event date, creation date, duration of the event, sport type, event owner, age, coordinates, skill levels

- Make relative imports absolute

- Add unittests for event search functionality
- Configure test database
- Convert relative imports to absolute imports in serializers.py

- Add testing command to run tests before starting application
- Add wait_for_db script for backend service to wait until database is ready

test_filter_by_date was failing due to the default value of the date field in EventPost model. By quoting the related part about auto_now_add from django documentation:
" So even if you set a value for this field when creating the object, it will be ignored."

Since the dates specified for the sample events created for tests were ignored, date_by_filter test was failing. This bug would cause wrong event dates while user creating an event, it is fixed by changing default value to the time of the event creation.