Update to typeorm 2.1.17 breaks indices

[kiwikern]

There have been a couple of changes to mongodb indices. This update breaks the indices:

2019-05-14T23:31:39.268+0200 E INDEX [TTLMonitor] ttl indexes require the expireAfterSeconds field to be numeric but received a type of null, sk
ipping ttl job for: { v: 2, unique: true, key: { userId: 1 }, name: "IDX_ca94189f5dcaefdae0d98de623", ns: "shassi_test.telegram-user-ids", sparse:
false, background: false, expireAfterSeconds: null }

https://github.com/typeorm/typeorm/blob/master/CHANGELOG.md#0217-2019-05-01