[DMS-938] Emit Project Schemas + Resource/Extension Tables + Abstract Identity Tables/Views

[simpat-adam]

Summary

This PR implements the DDL emission infrastructure for the relational model backend redesign, enabling generation of database schemas for PostgreSQL and MSSQL dialects.

Key Features

• Schema Emission: Generates CREATE SCHEMA statements for Ed-Fi project schemas (e.g., edfi, sample, tpdm)
• Resource/Extension Table Emission: Emits CREATE TABLE statements for resource root tables and extension tables with proper column types, constraints, and foreign keys
• Abstract Identity Tables/Views: Generates abstract identity tables and union views for polymorphic resource references
• Trigger Infrastructure: Implements discriminated union pattern (TriggerKindParameters) for trigger variants:
  • DocumentStamping - timestamp maintenance triggers
  • ReferentialIdentityMaintenance - referential identity sync triggers
  • AbstractIdentityMaintenance - abstract identity table maintenance
  • IdentityPropagationFallback - fallback propagation triggers
• Index Inventory: Derives and emits indexes for foreign key support and query optimization
• Key Unification Pass: Implements key unification for merged identity columns across resource hierarchies
• Constraint Derivation: Adds descriptor foreign key constraints and reference constraints with proper CHECK constraints

Technical Changes

• RelationalModelDdlEmitter - Main DDL emitter using SqlWriter for phased emission
• DeriveTriggerInventoryPass - Derives trigger inventory with proper reverse reference tracking
• KeyUnificationPass - Implements column aliasing and identity propagation
• DerivedModelSetManifestEmitter - JSON manifest emission for derived model set
• Extensive golden tests for both PostgreSQL and MSSQL DDL output
• PageDocumentIdSqlCompiler - SQL compiler for paginated document queries

Testing

• DDL emission golden tests comparing expected vs actual SQL for both dialects
• Authoritative relational model golden tests updated for new schema structure
• Unit tests for all new passes and emitters

Test plan

• Verify unit tests pass: dotnet test in backend projects
• Review golden test outputs for correctness
• Verify DDL emission produces valid SQL for both PostgreSQL and MSSQL

🤖 Generated with Claude Code

[simpat-adam]

This is the big guy. Emit schemas, tables, indexes, views, triggers

[simpat-adam]

Not sure why these didn't get alphabetized until my branch. Same goes for all the files under Old.Postgresql

[simpat-adam]

Yay Discriminated union

[simpat-adam]

Lots of changes in this file. Summary of DeriveTriggerInventoryPass changes:

The major change here is correcting the IdentityPropagationFallback trigger placement to align with the design specification in reference/design/backend-redesign/epics/01-relational-model/07-index-and-trigger-inventory.md (lines 97-102):

"For eligible targets (abstract targets and concrete targets with allowIdentityUpdates=true), inventory emits one propagation trigger per referenced table (TriggerTable) with deterministic referrer fan-out actions."

Before (incorrect): Triggers were placed on the referrer table (e.g., TR_Enrollment_Propagation_School on Enrollment). This resulted in N triggers for N referrers pointing to the same target.

After (per design): A single trigger is placed on the referenced table (e.g., TR_School_PropagateIdentity on School) that fans out to update all referrer tables. This is more efficient and matches where identity changes originate.

Other changes:

• Replaced DbTriggerKind enum with TriggerKindParameters discriminated union to carry trigger-specific metadata (identity elements, column mappings, referrer updates) needed for DDL emission
• Added BuildReverseReferenceIndex to collect all referrers per target resource
• Enhanced ReferentialIdentityMaintenance and AbstractIdentityMaintenance triggers with UUIDv5 computation metadata (resource key IDs, identity element mappings, superclass alias info)

The test changes reflect the corrected trigger placement — assertions now expect triggers on the referenced table with ReferrerUpdates containing the fan-out targets.