Move DocumentStores to Integrations

[bilgeyucel]

Tasks

Beta Give feedback

1. Prepare a guideline on "Creating a Document Store" https://github.com/deepset-ai/devrel-board/issues/73
2. Contact providers for the ownership
3. Collaboration of core&devrel for creating integrations
4. Start the deprecation process
5. Create a testing package for external document stores https://github.com/deepset-ai/devrel-board/issues/73

[bilgeyucel]

Some items in the issue are deprecated but here's what we have done so far:

• We have template repository for 2.0 Document Stores: https://github.com/deepset-ai/document-store/tree/main
• We are in touch with the providers
• All existing DocumentStores has a page on Haystack Integrations
  • The behavior will be the same for 2.0 Document Stores