Close datastore iterators to release underlying rows and Firestore resources on decode errors

[vanshika2720]

What this PR does:

Adds explicit resource cleanup to datastore.Iterator so underlying MySQL and Firestore iterators are closed when datastore iteration completes or exits early due to an error. All List() callers now defer iterator cleanup, and tests verify that Close() is called on both successful and error paths.

Why we need it:

Previously, datastore.Iterator had no Close() method, so an early return caused by a decode/scan error could leave the underlying sql.Rows or Firestore DocumentIterator open. Repeated failures could accumulate unreleased database resources and potentially exhaust available connections.

Which issue(s) this PR fixes:

Fixes #7219

Does this PR introduce a user-facing change?:

• How are users affected by this change: No direct user-facing behavior change. This fixes datastore resource cleanup and prevents database/Firestore resources from remaining open after iterator errors.
• Is this breaking change: No.
• How to migrate (if breaking change): Not applicable.

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[Copilot]

Pull request overview

This PR improves PipeCD’s datastore layer by adding explicit iterator cleanup, ensuring underlying MySQL sql.Rows and Firestore DocumentIterator resources are released even when iteration exits early due to decode/scan errors. This aligns iterator lifecycle management with how PipeCD continuously polls datastore lists and reduces risk of connection/resource exhaustion under repeated failures.

Changes:

• Extend datastore.Iterator with Close() error and implement it for MySQL and Firestore iterators.
• Ensure datastore store List() implementations and integration test iteration helpers defer it.Close() after successful Find().
• Update gomock iterator mock and unit tests to assert Close() is invoked on both success and error paths.

Reviewed changes

Copilot reviewed 27 out of 28 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pkg/datastore/datastore.go	Adds Close() error to the Iterator interface with lifecycle guidance.
pkg/datastore/mysql/iterator.go	Implements Close() by closing underlying sql.Rows.
pkg/datastore/firestore/iterator.go	Implements Close() by stopping the underlying Firestore DocumentIterator.
pkg/datastore/mock.go	Regenerates/updates gomock to include Iterator.Close().
pkg/datastore/projectstore.go	Defers iterator close in List() to ensure cleanup.
pkg/datastore/pipedstore.go	Defers iterator close in List().
pkg/datastore/eventstore.go	Defers iterator close in List().
pkg/datastore/deploymenttracestore.go	Defers iterator close in List().
pkg/datastore/deploymentstore.go	Defers iterator close in List().
pkg/datastore/deploymentchainstore.go	Defers iterator close in List().
pkg/datastore/commandstore.go	Defers iterator close in List().
pkg/datastore/applicationstore.go	Defers iterator close in List().
pkg/datastore/apikey.go	Defers iterator close in List().
pkg/datastore/projectstore_test.go	Updates expectations to assert Close() is called.
pkg/datastore/pipedstore_test.go	Updates expectations to assert Close() is called.
pkg/datastore/deploymentstore_test.go	Updates expectations to assert Close() is called.
pkg/datastore/commandstore_test.go	Updates expectations to assert Close() is called.
pkg/datastore/applicationstore_test.go	Updates expectations to assert Close() is called.
pkg/datastore/apikey_test.go	Updates expectations to assert Close() is called.
test/integration/datastore/mysql/project_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/piped_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/event_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/deploymentchain_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/deployment_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/command_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/application_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/mysql/apikey_test.go	Defers iterator close in test helper iteration.
test/integration/datastore/firestore/firestore_test.go	Defers iterator close in test helper iteration.

Files not reviewed (1)

• pkg/datastore/mock.go: Generated file

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[vanshika2720]

@mohammedfirdouss