refactor: enhance Prisma schema with PostgreSQL optimizations and data integrity

- Add PostgreSQL-specific data types (@db.VarChar, @db.Text, @db.Timestamptz, @db.JsonB, @db.Inet)
- Implement comprehensive database constraints via custom migration
- Add detailed field-level documentation and enum descriptions
- Optimize indexes for common query patterns and company-scoped data
- Ensure data integrity with check constraints for positive values and logical time validation
- Add partial indexes for performance optimization on failed/pending processing sessions

prisma/migrations/20241228000001_add_data_integrity_constraints/migration.sql

@@ -0,0 +1,91 @@
+-- Custom migration for PostgreSQL-specific data integrity constraints
+-- These constraints cannot be expressed in Prisma schema directly
+
+-- Ensure only one default AI model per company
+CREATE UNIQUE INDEX "unique_default_ai_model_per_company" 
+ON "CompanyAIModel" ("companyId") 
+WHERE "isDefault" = true;
+
+-- Ensure positive token counts in AI processing requests
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "positive_prompt_tokens" CHECK ("promptTokens" >= 0);
+
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "positive_completion_tokens" CHECK ("completionTokens" >= 0);
+
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "positive_total_tokens" CHECK ("totalTokens" >= 0);
+
+-- Ensure positive costs
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "positive_prompt_cost" CHECK ("promptTokenCost" >= 0);
+
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "positive_completion_cost" CHECK ("completionTokenCost" >= 0);
+
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "positive_total_cost" CHECK ("totalCostEur" >= 0);
+
+-- Ensure session times are logical
+ALTER TABLE "Session" 
+ADD CONSTRAINT "logical_session_times" CHECK ("endTime" >= "startTime");
+
+-- Ensure positive response times
+ALTER TABLE "Session" 
+ADD CONSTRAINT "positive_response_time" CHECK ("avgResponseTime" IS NULL OR "avgResponseTime" >= 0);
+
+-- Ensure positive message counts
+ALTER TABLE "Session" 
+ADD CONSTRAINT "positive_message_count" CHECK ("messagesSent" IS NULL OR "messagesSent" >= 0);
+
+ALTER TABLE "SessionImport" 
+ADD CONSTRAINT "positive_message_count_import" CHECK ("messagesSent" IS NULL OR "messagesSent" >= 0);
+
+-- Ensure positive response times in imports
+ALTER TABLE "SessionImport" 
+ADD CONSTRAINT "positive_response_time_import" CHECK ("avgResponseTimeSeconds" IS NULL OR "avgResponseTimeSeconds" >= 0);
+
+-- Ensure positive token values in imports
+ALTER TABLE "SessionImport" 
+ADD CONSTRAINT "positive_tokens_import" CHECK ("tokens" IS NULL OR "tokens" >= 0);
+
+ALTER TABLE "SessionImport" 
+ADD CONSTRAINT "positive_tokens_eur_import" CHECK ("tokensEur" IS NULL OR "tokensEur" >= 0);
+
+-- Ensure positive message order
+ALTER TABLE "Message" 
+ADD CONSTRAINT "positive_message_order" CHECK ("order" >= 0);
+
+-- Ensure positive retry counts
+ALTER TABLE "SessionProcessingStatus" 
+ADD CONSTRAINT "positive_retry_count" CHECK ("retryCount" >= 0);
+
+-- Ensure logical processing times
+ALTER TABLE "SessionProcessingStatus" 
+ADD CONSTRAINT "logical_processing_times" CHECK ("completedAt" IS NULL OR "startedAt" IS NULL OR "completedAt" >= "startedAt");
+
+-- Ensure logical AI request times
+ALTER TABLE "AIProcessingRequest" 
+ADD CONSTRAINT "logical_ai_request_times" CHECK ("completedAt" IS NULL OR "completedAt" >= "requestedAt");
+
+-- Ensure logical pricing date ranges
+ALTER TABLE "AIModelPricing" 
+ADD CONSTRAINT "logical_pricing_dates" CHECK ("effectiveUntil" IS NULL OR "effectiveUntil" > "effectiveFrom");
+
+-- Ensure positive max tokens for AI models
+ALTER TABLE "AIModel" 
+ADD CONSTRAINT "positive_max_tokens" CHECK ("maxTokens" IS NULL OR "maxTokens" > 0);
+
+-- Ensure logical user reset token expiry
+ALTER TABLE "User" 
+ADD CONSTRAINT "logical_reset_token_expiry" CHECK ("resetTokenExpiry" IS NULL OR "resetToken" IS NOT NULL);
+
+-- Add partial index for failed processing sessions (PostgreSQL-specific optimization)
+CREATE INDEX CONCURRENTLY "sessions_failed_processing" 
+ON "SessionProcessingStatus" ("sessionId") 
+WHERE "status" = 'FAILED';
+
+-- Add partial index for pending processing sessions
+CREATE INDEX CONCURRENTLY "sessions_pending_processing" 
+ON "SessionProcessingStatus" ("stage", "status") 
+WHERE "status" = 'PENDING';