title: Cosmos DB trigger - Shared throughput collection should have a partition key
body: <p>I have an Azure Function with a Cosmos DB trigger configured to auto-create a lease collection on-demand, I get the following error when running against a Cosmos DB with throughput configured at database level</p>
  
  <blockquote>
    <p>[30/11/2018 23:33:04] Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.Foo'. Microsoft.Azure.WebJobs.Extensions.CosmosDB: Cannot create Collection Information for X in database Y with lease leases in database Y : Shared throughput collection should have a partition key</p>
  </blockquote>
  
  <p>Works absolutely fine when the throughput is solely configured at container level. Also tried manually creating a lease collection and setting <code>id</code> as the partition key (given from my other DB it looked like all a lease has was an <code>id</code> / <code>ttl</code>) but then it complains about the PK not being provided.</p>
  
  <p>Any ideas?</p>