Section parsing places metadata for Assign in content field

[campb303]

Section parsing will place the metadata of an assignment inside of a content entry. These details should be their own entries.

Example: current behavior (from ce 8):

    {
      "type": "assign",
      "content": [
        {
          "by": "remender",
          "datetime": "2020-03-11T09:26:25-0400",
          "to": "remender"
        }
      ]
    },

Example: expected behavior (for ce 8):

    {
      "type": "assign",
      "by": "remender",
      "datetime": "2020-03-11T09:26:25-0400",
      "to": "remender"
    },

[campb303]

This was fixed in this commit.