Feature/graph refactor

[jamesrichards4]

The graph structure is currently messy and confusing. By imposing rules and constraints we can tidy it up and make it easier to develop in future.

• There is a single shape of state object: RedboxState
• Nodes have three types and are named for them: p_rocess, d_ecision, and s_send
• Process nodes are composed by a simple suite of patterns
• We build subgraphs from these building blocks
• We build the graph from these subgraphs
• We test at each level: pattern, subgraph and graph

I'm a visual learner

Changes proposed in this pull request

• Adds a single RedboxState state and a custom document_reducer function
• Adds redbox.graph.nodes.processes for processes and patterns
• Adds redbox.graph.nodes.sends for sends
• Adds redbox.graph.edges for functions that build conditionals, which attach to decisions
• Adds redbox.graph.root for subgraphs and the final graph
• Unit tests added at the pattern and graph levels
• Adds a README to explain some design conventions to follow

Guidance to review

• Read the README
• Review processes and sends
• Review edges
• Review root
• Review everything else

Things to check

• [x] I have added any new ENV vars in all deployed environments
• [x] I have tested any code added or changed
• [x] I have run integration tests

[jamesrichards4]

Raising this to get thoughts on how well this ties in with what Will originally planned. This already seems way neater and more extensible. The visualisation is massively improved:

from IPython.display import Image, display
from langchain_core.runnables.graph import CurveStyle, MermaidDrawMethod, NodeStyles

display(
    Image(
        app = Redbox(env=Settings(_env_file="../.env")).graph.get_graph().draw_mermaid_png(
            draw_method=MermaidDrawMethod.API,
        )
    )
)

[jamesrichards4]

@wpfl-dbt be great to get your thoughts on this, the redbox tests are failing for coverage but once I merge main I can remove some worker only code which should sort that so this is good to go (might need additional tests anyway but we can chat about that)