Description

Closes: #1637

Adds automated coverage that a Helm upgrade from a prior release to the current build is safe: migrations apply cleanly, existing data survives, the resulting schema matches a fresh install, and the migrations reverse cleanly. Also covers the rolling-deploy window where prior-release pods serve against an already-migrated schema.

Tests

• Upgrade round-trip (TestUpgrade, gated by RUN_UPGRADE_TESTS): installs the prior release, seeds representative data, upgrades to the current build, then asserts the controller rolls out without crashing, migrations reach the target version cleanly, the seeded data survives, the upgraded schema is identical to a clean install, and reversing the migrations restores the prior schema with data intact.
• Rolling compatibility (TestRollingUpgradeCompatibility, gated by RUN_ROLLING_UPGRADE_TESTS): runs the upgrade with two controller replicas and verifies a prior-release pod can still read and write while the new schema is live. Skips when there is no migration delta to exercise.

Targets

Both tests run against two prior versions (a CI matrix, deduplicated when they coincide):

• the latest release reachable from HEAD — the adjacent previous release, and
• the previous stable line's latest patch (the release/vX.Y.x tip) — the supported rollback floor.

Override locally with UPGRADE_FROM_VERSION.

Running locally

Requires a kind cluster, then:

make create-kind-cluster
make run-upgrade-tests

or

make create-kind-cluster
make run-rolling-upgrade-tests

A run leaves the database migrated, so recreate the cluster between runs.

Notes

• When the current and prior releases share the same migration set, the migration and reversal assertions are no-ops (the data-survival, schema-equivalence, and no-crash checks still run); the tests engage fully on the first new migration. The two targets also coincide today and diverge once a new minor releases or the stable line gets a backport patch.
• Query-level backward compatibility (a prior release's queries against the new schema) is covered separately by a static check in Add query-contraction check against the previous release #2085.
• This branch carries its own copies of the helper scripts, which are shared with Add query-contraction check against the previous release #2085, so that will require a trivial merge conflict resolution.