feat: support seperate memory

[fatelei]

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Summary

fix #13738 support seperate memory config

Screenshots

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Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[gemini-code-assist]

Summary of Changes

Hello @fatelei, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the memory management capabilities within the application's workflow nodes, particularly for LLM nodes. It introduces a new concept of 'independent' memory, allowing each node to maintain its own conversational context separate from the main conversation's shared memory. This provides developers with greater flexibility to design complex workflows where memory isolation or transient memory states are required, addressing the need for more sophisticated memory handling in AI applications.

Highlights

• Separate Memory Configuration: Introduced the ability to configure memory as either 'shared' (conversation-wide) or 'independent' (per-node), providing more granular control over memory management within workflows.
• Node-Scoped Memory Implementation: Added NodeScopedMemory to handle independent memory, which is persisted as a ConversationVariable and can be optionally cleared after a node's execution.
• Frontend UI Updates: The workflow editor's memory configuration UI now includes options to select the memory mode (shared/independent) and a toggle to clear independent memory after execution.
• Memory Abstraction: A new ChatHistoryMemory protocol was introduced to abstract the memory interface, allowing both TokenBufferMemory (shared) and NodeScopedMemory (independent) to be used interchangeably where chat history is needed.

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[gemini-code-assist]

Code Review

This pull request introduces a valuable feature by adding support for node-specific, independent memory scopes in workflows. The implementation is solid, with good use of a Protocol for different memory types and corresponding UI changes. I've identified a few areas for improvement, mainly related to performance optimization by avoiding an unnecessary database query and enhancing code clarity and type safety. Overall, this is a great addition.