Unable to fully configure exploration summarization

[seancolsen]

Summarization transforms are broken in a weird way. Adding a summarization transformation hides all but the selected column. And the UI to configure the aggregation is missing.

master branch	explorations branch

[seancolsen]

@Anish9901 I've spent some more time troubleshooting this, and I think it's likely a backend bug. So I'd like you to look into it next to see if you can identify a fix.

Here are my reproduction steps.

1. Run off my explorations branch and off master (e.g. via our internal site) for comparison.

2. Begin an exploration using the Authors table in our library data.

3. Add the First Name column and the id column (in that order).

4. Add a summarization transformation.

5. Observe that the API requests are essential identical across the two versions (except for some minor differences due to RPC migration and attnums/oids).

6. Observe that the API responses differ in two important ways:

   • Return records have missing columns. (Compare the entries in records.results.)

   • Returned output columns list is missing columns.

     In master, output_columns is:

     [
       "Authors_First Name_grouped",
       "Authors_id_agged"
     ]

     In explorations, output_columns is:

     [
       "Authors_First Name_grouped"
     ]

     I think the missing UI may be due to there only being a single entry in the returned output_columns array.

[seancolsen]

#3884 seems to fix the backend problems described in this issue, so I'm allowing that PR to close this issue when it's merged.

However during my testing I identified that there still appears to be a front end issue here. I've opened #3887 to track that.