community: update Memgraph integration

[katarinasupe]

Description:

• Memgraph no longer relies on Neo4jGraphStore but implements GraphStore, just like other graph databases.
• Memgraph no longer relies on GraphQAChain, but implements MemgraphQAChain, just like other graph databases.
• The refresh schema procedure has been updated to try using SHOW SCHEMA INFO. The fallback uses Cypher queries (a combination of schema and Cypher) → LangChain integration no longer relies on MAGE library.
• The schema structure has been reformatted. Regardless of the procedures used to get schema, schema structure is the same.
• The add_graph_documents() method has been implemented. It transforms GraphDocument into Cypher queries and creates a graph in Memgraph. It implements the ability to use baseEntityLabel to improve speed (baseEntityLabel has an index on the id property). It also implements the ability to include sources by creating a MENTIONS relationship to the source document.
• Jupyter Notebook for Memgraph has been updated.
• Issue: /
• Dependencies: /
• Twitter handle: supe_katarina

I initially had all imports in langchain package as well, since I followed the implementation of others, but now I removed it based on the PR template.

I also ran make format and make lint, but based on the PR template, I didn't want to commit changes on other integrations. Let me know if that's okay.

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Name	Status	Preview	Comments	Updated (UTC)
langchain	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 1, 2024 0:18am

[katarinasupe]

Hi @baskaryan, tagging as noted in PR template. Please let me know what I need to do regarding the test and what's needed to do in order to get this merged.