fix: retrieve ingestion logs with null change set

[mfiedorowicz]

When change set is not being created, for example due to unreachable NetBox, postgres view returns NULL value and row scanning cannot cast to type value:

can't scan into dest[15]: cannot scan NULL into *postgres.ChangeSet

We can solve this by changing ChangeSet type to pointer with sqlc config.

[github-actions]

Go test coverage

STATUS	ELAPSED	PACKAGE	COVER	PASS	FAIL	SKIP
🟢 PASS	0.00s	github.com/netboxlabs/diode/diode-server/dbstore/postgres	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/diode/diode-server/gen/dbstore/postgres	0.0%	0	0	0
🟢 PASS	1.21s	github.com/netboxlabs/diode/diode-server/ingester	71.2%	9	0	0
🟢 PASS	1.05s	github.com/netboxlabs/diode/diode-server/migrator	68.2%	4	0	0
🟢 PASS	0.01s	github.com/netboxlabs/diode/diode-server/netbox	0.0%	0	0	0
🟢 PASS	1.60s	github.com/netboxlabs/diode/diode-server/netboxdiodeplugin	78.9%	42	0	0
🟢 PASS	1.43s	github.com/netboxlabs/diode/diode-server/reconciler	83.2%	49	0	0
🟢 PASS	1.09s	github.com/netboxlabs/diode/diode-server/reconciler/applier	81.8%	1	0	0
🟢 PASS	0.01s	github.com/netboxlabs/diode/diode-server/reconciler/changeset	0.0%	0	0	0
🟢 PASS	1.30s	github.com/netboxlabs/diode/diode-server/reconciler/differ	80.3%	81	0	0
🟢 PASS	1.02s	github.com/netboxlabs/diode/diode-server/server	85.7%	14	0	0
🟢 PASS	1.01s	github.com/netboxlabs/diode/diode-server/version	100.0%	1	0	0

Total coverage: 74.8%