feat(orm): add async Eloquent-style upsert()

[bedus-creation]

Summary

Adds an async, Eloquent-style upsert() to the masoniteorm ORM. It emits a single bulk statement and is dialect-correct across postgres, sqlite, and mysql via SQLAlchemy dialect insert helpers.

• postgres / sqlite: INSERT ... ON CONFLICT (unique_by) DO UPDATE SET col = excluded.col
• mysql: INSERT ... ON DUPLICATE KEY UPDATE col = VALUES(col)

API

await User.upsert(values, unique_by, update=None)          # Model async classmethod
await User.query().upsert(values, unique_by, update=None)  # QueryBuilder

• values: dict | list[dict]
• unique_by: str | list[str] (conflict target)
• update: columns to write on conflict — defaults to every provided column except the unique_by keys
• returns the affected rowcount

Behavior

• Single statement: built with sqlalchemy.dialects.{postgresql,sqlite,mysql}.insert().values([...]) so multiple rows compile to one multi-row VALUES + conflict clause.
• Casts: each row is run through the model Caster.set (same set-cast behavior as the insert path).
• Timestamps: kept consistent with the current insert() path per PM ruling — no auto-injection on INSERT. Explicit created_at/updated_at in a row dict are honored; updated_at is refreshed on the DO UPDATE branch only when __timestamps__ is enabled and the model declares updated_at.
• Execution: new Connection.upsert(statement) runs the prepared Core construct and returns rowcount.

Files

Change	File
M	masoniteorm/models/builder.py — upsert() + _build_upsert_statement()
M	masoniteorm/models/model.py — Model.upsert() classmethod
M	masoniteorm/connections/connection.py — Connection.upsert()
A	tests/masoniteorm/sqlite/builder/test_sqlite_builder_upsert.py (live)
A	tests/masoniteorm/mysql/builder/test_mysql_builder_upsert.py (SQL-compile)
A	tests/masoniteorm/postgres/models/test_upsert.py (live, skippable)

Tests

• uv run pytest --ignore=tests/masoniteorm/postgres --cov → 1501 passed, 7 skipped, coverage 66.79% (above fail_under).
• sqlite upsert + mysql compile suites: 8 passed.
• Postgres suite mirrors existing postgres tests (needs a live server; CI provides one — locally skipped via --ignore).
• ruff check / ruff format --check: clean.

Note for follow-up

While grounding this work I found the model save path never fires the creating event, so created_at/updated_at are not auto-injected on insert today (confirmed by test_observers.py). This PR intentionally does not fix that latent bug — it stays consistent with the existing insert() path. Flagging for a separate follow-up task.

🤖 Generated with Claude Code