Add some controls to the user list (BE)

[eviltwinhans]

Description

The user list on Web UI may be large, so we need to be able to filter it:

• By role - add a dropdown to choose a role we are interested in
• By sign up date - add a control which allows us to select those signed up
  • before the date
  • after the date
  • between two dates
• By quotas - add a control which allows us to select users with credits
  • more than a give value
  • less than a given value
  • within a range

Tasks

• Make backend api supporting Web UI user filters
• Add a comment to https://github.com/neuro-inc/platform-web-ui/issues/503 to unblock it

[dalazx]

@eviltwinhans why platform-api?

[eviltwinhans]

@dalazx, this FE feature requires changes on BE side as well.