Refactor: Share Knex Connections between Tenants

[nh758]

#100

Requirements

1. Use a single Knex client per service

Tasks

• Write Documentation

Reference

Max Connections Scaling
Can use Knex .withSchema() to set the Tenant DB.

Knex.queryBuilder().withSchema(tenantDB).select() //...
Knex.schema.withSchema(tenantDB).createTable(cb) 

In Objection it should be possible to do this when creating a custom Model. See Vincit/objection.js#85 (comment)