feat(slack): adds canvas support for Slack channels

[whitdog47]

This PR adds comprehensive Slack Canvas integration to Dispatch, enabling automatic creation and management of participants canvases for both incidents and cases. The feature provides real-time visibility of participants in incident and cases with dedicated Slack channels and automatic role updates.

Key Features

Slack Canvas API Integration

• Added new Slack Canvas API endpoints to the plugin enums
• Implemented create_canvas, edit_canvas, and delete_canvas functions in the Slack service
• Added robust error handling with graceful degradation (logs errors instead of re-raising)

Participants Canvas Management

• Automatic Creation: Canvas created when incidents/cases are created (after participants resolved)
• Real-time Updates: Canvas updated when participants are added, removed, or roles change
• Role-based Organization: Participants grouped by role with dynamic headings (e.g., "Incident Commander" vs "Incident Commanders")
• Empty State Handling: Shows "No participants" message when no participants exist

Database Integration

• Created new Canvas SQLAlchemy model with TimeStampMixin and ProjectMixin
• Added CanvasType enum with participants type
• Implemented full CRUD operations in canvas/service.py
• Added bidirectional relationships to Incident.canvases and Case.canvases

Lifecycle Integration

• Incident Flows: Canvas created in incident_create_resources, updated in participant flows
• Case Flows: Canvas created in case_create_resources_flow, updated in participant flows
• Self-healing: Canvas automatically recreated if missing during updates
• Error Resilience: Participant processing errors don't break canvas creation

Robust Error Handling

• Added comprehensive safety checks for conversation and channel_id existence
• Implemented graceful error handling in case creation flows
• Canvas operations continue even if participant processing fails
• All errors logged with appropriate levels (DEBUG, WARNING, ERROR)

Technical Implementation

Canvas Content Generation

• Role-based sorting with priority: Incident Commander > Scribe > Reporter > Participant > Observer
• Dynamic pluralization of role headings (e.g., "Incident Commander" vs "Incident Commanders")
• Clean bulleted list format for easy reading
• Handles empty participant lists gracefully

Permission Management

• Incidents: Incident Commander gets edit permissions
• Cases: Case Assignee gets edit permissions
• Canvas locked to specific users to prevent unauthorized edits

Integration Points

• Incident Creation: Canvas created after all participants resolved
• Participant Addition: Canvas updated when new participants added
• Participant Removal: Canvas updated when participants removed
• Role Assignment: Canvas updated when roles change

Files Changed

New Files

• src/dispatch/canvas/ - New canvas package
  • models.py - Canvas SQLAlchemy model
  • service.py - CRUD operations
  • enums.py - CanvasType enum
  • flows.py - Canvas creation/update logic

Modified Files

• src/dispatch/plugins/dispatch_slack/
  • enums.py - Added Canvas API endpoints
  • service.py - Added canvas API functions
  • plugin.py - Added canvas methods to plugin instance
• src/dispatch/incident/flows.py - Integrated canvas creation/updates
• src/dispatch/case/flows.py - Integrated canvas creation/updates
• src/dispatch/incident/models.py - Added canvases relationship
• src/dispatch/case/models.py - Added canvases relationship

[Copilot]

Pull Request Overview

This PR adds comprehensive Slack Canvas integration to Dispatch, enabling automatic creation and management of participants canvases for both incidents and cases. The feature provides real-time visibility of participants with dedicated Slack canvases and automatic role updates.

• Implements new Slack Canvas API endpoints with create, edit, and delete functionality
• Creates database models and CRUD operations for canvas management
• Integrates canvas lifecycle management into incident and case flows with automatic creation and updates

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/dispatch/plugins/dispatch_slack/service.py	Added Canvas API functions and updated string formatting
src/dispatch/plugins/dispatch_slack/plugin.py	Added Canvas methods to plugin instance
src/dispatch/plugins/dispatch_slack/enums.py	Added Canvas API endpoints
src/dispatch/incident/models.py	Added canvases relationship
src/dispatch/incident/flows.py	Integrated canvas creation and update flows
src/dispatch/database/revisions/tenant/versions/2025-08-28_ff08d822ef2c.py	Database migration for canvas table
src/dispatch/case/models.py	Added canvases relationship
src/dispatch/case/flows.py	Integrated canvas creation and update flows
src/dispatch/canvas/service.py	CRUD operations for canvas management
src/dispatch/canvas/models.py	SQLAlchemy model and Pydantic schemas
src/dispatch/canvas/flows.py	Canvas creation and update business logic
src/dispatch/canvas/enums.py	Canvas type enumeration
src/dispatch/canvas/init.py	Module initialization
src/dispatch/init.py	Added canvas model import

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[jneelamekam]

@whitdog47 : The changes look good to me.