expand lecturer API with storage and retrieval of consulations, timetables

## Summary
Expand the lecturer model and implement a synchronization mechanism to process and store complex data (consultations, timetables) supplied by the providers.

## [Acceptance criteria](https://www.atlassian.com/work-management/project-management/acceptance-criteria)
- [ ] Expand the `Lecturer` aggregate with consultations and a timetable collections.
- [ ] Create a command and use case for synchronization that calls the providers and updates the `Lecturer` aggregates in the db using `ILecturerRepository`.
- [ ] Update the endpoint from Issue 1 (Query) to correctly fetch and map the new sections (consultations, timetable, courses) into the resulting JSON.

## Notes
We do not query external providers on the fly when the frontend calls our API. Instead, the command created in this task (that can be scheduled by a cron job) processes, merges data from various sources, and saves it in our db. This keeps our endpoint fast and immune to external systems outages.