feature(api,pkg): add migrations to convert recorded sesisons into Asciinema

To be able to use our recorded sessions as Asciinema files, we migrated
registers from this collection into session's events', turning them into
events of a session, as others SSH request types, deleting the older
collection, `recorded_sessions`, from the database. With events, we
can sort and process them easily into the Asciinema records, as we can
obtain all data needed in one single collection.

Author: henrybarreto

api/store/mongo/migrations/main.go

@@ -103,6 +103,9 @@ func GenerateMigrations() []migrate.Migration {
 		migration91,
 		migration92,
 		migration93,
+		migration94,
+		migration95,
+		migration96,
 	}
 }