[SERVICES-2370] Pairs query pagination, sorting and filtering

[mad2sm0key]

Reasoning

• provide a Relay-compliant query for fetching pairs data

Proposed Changes

• create new filterablePairs query that follows the GraphQL "Connections" specification
• extract pair filtering logic in a separate service

How to test

query {
  filterablePairs(
    filters:{
      minTradesCount:50
      minVolume:200
    }
    pagination:{
      first:10
    }
    sorting: {
      sortField:TRADES_COUNT
      sortOrder:DESC
    }
  ) {
    edges {
      cursor
      node {
        address
        firstToken {
          identifier
        }
        secondToken {
          identifier
        }
        tradesCount
        volumeUSD24h
      }
    }
    pageInfo {
      startCursor
      endCursor
      hasNextPage
      hasPreviousPage
    }
    pageData {
      count
      limit
      offset
    }
  }
}

[cfaur09]

Tests 🟢
Observation:

• minTradesCount field need to be integer