Missing index names

[PVince81]

oc_notifications have indices with missing names when setup from scratch:

  KEY `IDX_16B80748C96E70CF` (`app`),
  KEY `IDX_16B807488D93D649` (`user`),
  KEY `IDX_16B80748A5D6E63E` (`timestamp`),
  KEY `IDX_16B8074811CB6B3A232D562B` (`object_type`,`object_id`)

should be, which appears only when upgrading

  KEY `oc_notifications_app` (`app`),
  KEY `oc_notifications_user` (`user`),
  KEY `oc_notifications_timestamp` (`timestamp`),
  KEY `oc_notifications_object` (`object_type`,`object_id`)

Something might be wrong with the migrations.

We should add an extra migration to properly create the indices with names for initial setup, which should not affect performance.