Create Postgres migration for graph schema and identity storage

[wendellmva]

Issue: Create Postgres migration for graph schema and identity storage

Summary

Create and run EF Core migrations in sourcelib to establish the complete database schema for the graph database including nodes, edges, types, properties, and graph-based identity storage.

Goals

• Generate EF Core migration for all graph entities
• Include identity/auth tables from graph-based identity work
• Run migration against Postgres database
• Verify schema correctness

Scope

1. Create migration for core graph entities:
   • NodeTypes, EdgeTypes
   • Nodes, Edges
   • Properties (with discriminator support)
   • Indexes and constraints
2. Include graph-based identity storage:
   • Users, Roles, Claims (as graph nodes/edges)
   • Login providers, Tokens, Refresh tokens
3. Run migration against local Postgres instance
4. Verify tables, indexes, and relationships
5. Test basic CRUD operations

Acceptance Criteria

• Migration files generated in sourcelib project
• Migration runs successfully against Postgres
• All tables created with correct schema
• Indexes and foreign keys properly configured
• Can perform basic CRUD operations on all entities
• Identity data can be stored and retrieved from graph

Dependencies

• Postgres database running locally or in dev environment
• EF Core tools installed
• GraphContext configured for Postgres

Technical Notes

• Use Npgsql provider for Postgres
• Ensure connection string is configured
• Consider seed data for initial node/edge types
• Document migration commands in README

Checklist

• Configure Postgres connection string
• Generate EF Core migration
• Review migration SQL
• Run migration against database
• Verify schema in database
• Test CRUD operations
• Document migration process

References

• Issue Replace IdentityGraphContext with GraphContext-based identity storage #99: Graph-based identity storage
• SPEC0200-0204: Core graph entities