UPSERT

• Add UPSERT functionality using PostgreSQL's INSERT ... ON CONFLICT ... DO UPDATE syntax:
  • New query.upsert() method generates upsert queries with configurable conflict targets
  • Supports single or multiple column conflict targets (e.g., 'id' or ['email', 'username'])
  • Properties with both INSERT and UPDATE operations are automatically included in upsert
  • Optionally includes consumerId and consumerName for history tracking
  • Supports RETURNING clause to retrieve updated/inserted row IDs
• Add upsert() Express middleware for handling upsert operations:
  • Expects rows and conflictTarget in request body
  • Returns upserted rows with IDs in res.locals.rows
  • Supports chunking for bulk operations
• Add convenience Express substack middlewares:
  • upsertArraySubstack: Returns [normalizeArray, validateArray, upsert] middleware chain
  • upsertOneSubstack: Returns [normalizeOne, validateOne, upsert] middleware chain