Improving admin ability to grant and revoke Plus. #1940

Closes #1940 (closed)

Depends on front!1485 (merged)

Testing

1. Log in as sandbox admin

2. Go to https://fix-admin-plus-granting-1940.minds.io/nemofin/

3. Enter sandbox cassandra cqlsh

• Useful commands:

kubectl exec -it cassandra-0 cqlsh

Check plus

select * from minds.entities where key='991463054707265537' and column1='plus_expires';`

Check pro

select * from minds.entities where key='991463054707265537' and column1='plus_expires';`

4. Make changes using the admin dropdown on my channel, check the value against https://www.epochconverter.com/