Topicer Interface - Support for using DB embeddings

[mdocekal]

I think we missed support for using database embeddings in discover_topics_in_db_* methods. The current state is as follows

@abstractmethod
  async def discover_topics_in_db_sparse(self, db_request: DBRequest, n: int | None = None) -> DiscoveredTopicsSparse:
      """
      Discover topics based on a database request and return a sparse representation.

      :param db_request: Database request to fetch texts for topic discovery.
      :param n: Optional number of topics to propose, if None uses the default value.
      :return: DiscoveredTopicsSparse
      """
      ...

  @abstractmethod
  async def discover_topics_in_db_dense(self, db_request: DBRequest, n: int | None = None) -> DiscoveredTopics:
      """
      Discover topics based on a database request and return a dense representation.

      :param db_request: Database request to fetch texts for topic discovery.
      :param n: Optional number of topics to propose, if None uses the default value.
      :return: DiscoveredTopics
      """
      ...

I believe we should have

@abstractmethod
  async def discover_topics_in_db_sparse(self, db_request: DBRequest, n: int | None = None, db_embeddings: bool | None = None) -> DiscoveredTopicsSparse:
      """
      Discover topics based on a database request and return a sparse representation.

      :param db_request: Database request to fetch texts for topic discovery.
      :param n: Optional number of topics to propose, if None uses the default value.
      :param db_embeddings: Obtain text representations from database, if None uses the default. 
      :return: DiscoveredTopicsSparse
      """
      ...

  @abstractmethod
  async def discover_topics_in_db_dense(self, db_request: DBRequest, n: int | None = None, db_embeddings: bool | None = None) -> DiscoveredTopics:
      """
      Discover topics based on a database request and return a dense representation.

      :param db_request: Database request to fetch texts for topic discovery.
      :param n: Optional number of topics to propose, if None uses the default value.
      :param db_embeddings: Obtain text representations from database, if None uses the default. 
      :return: DiscoveredTopics
      """
      ...

to allow usage of precomputed representations.