API returns column default value formatted differently from submitted

[seancolsen]

Steps to reproduce

1. Use the front end to set a default value for a text column. In the value field, enter:

   foo bar
   

2. Observe that the default is set up as expected in PostgreSQL.

3. Expect the "Default Value" configuration form for the column to display a default value of foo bar, exactly as-entered.

4. Instead, observe that the default value displayed in the form (as is returned from the API) is:

   'foo bar'::text
   

This bug presents usability problems for users wishing to modify an existing default value.

The default value can be modified, but it must first be extracted from within the text casting expression.

Considerations

I think a proper fix for this bug may require some re-thinking of the API return value schema when fetching columns. I'm not sure we'd be able to fix this while sticking to using a single string here.

[seancolsen]

I've confirmed this is a regression. The bug is not present in Mathesar 0.1.7.