Adding search, sorting, and filtering functionality to GET events

- Search (by term, so not just name, but maybe also description or keyword)
- Sort By:
- `start_date_time`
- `name`
- `coins`
- `max_volunteers`
Filter By:
- `organization`
- `age` (this could be null for some events, will add to db later)
By:
-  `EventType`
