text: Title: Handle edge case search queries better
  Body: We should do some preprocessing of `search_query` here to prevent errors in edge cases, e.g. where the query ends with an operator like `&` or `|`.
  
  Words separated by only a space and no operator also have no effect currently, we could modify these such that `&` is inserted automatically.
  
  List of valid operations I am aware of:
  
  ```
  &
  |
  <->
  !
  ```
  
  The syntax also allows combinations like `&!` and groupings via parantheses.
  
  https://github.com/LAION-AI/Open-Assistant/blob/main/backend/oasst_backend/prompt_repository.py#L1023