title: Are mutation methods required to be on the top level?
body: <p>All docs and tutorials usually show simple examples of mutations that look like this:</p>
  
  <pre><code>extend type Mutation {
    edit(postId: String): String
  }
  </code></pre>
  
  <p>But this way the <code>edit</code> method has to be unique across all entities, which to me seems like not a very robust way to write things. I would like to describe mutation similar to how we describe Queries, something like this:</p>
  
  <pre><code>type PostMutation {
    edit(postId: String): String
  }
  
  extend type Mutation {
    post: PostMutation
  }
  </code></pre>
  
  <p>This seems to be a valid schema (it compiles and I can see it reflected in the generated graph-i-ql docs). But I can't find a way to make resolvers work with this schema.</p>
  
  <p>Is this a supported case for GraphQL?</p>