Auth changes need to be reflected in Things and Users

[dborovcanin]

FEATURE REQUEST

1. Is there an open issue addressing this request? If it does, please add a "+1" reaction to the existing issue, otherwise, proceed to step 2. There is no such issue.

2. Describe the feature you are requesting, as well as the possible use case(s) for it. For listing purposes, some information about policies needs to be attached to Mainflux Thing. See #1507 for more information. To keep Things policy information in sync with updates on Auth service, each update needs to be either pushed to the message queue or sync with Things and Users services using RPC.

3. Indicate the importance of this feature to you (must-have, should-have, nice-to-have). This is a must-have.