NUMERIC, Scientific, NaN

A Postgresql NUMERIC value can be NaN, but a Haskell Scientific value cannot.

However, `numeric` links NUMERIC to Scientific. What can I do if I want to use NUMERIC columns with NaN values?

The next best thing I can do is to make the column nullable, but I would rather simply use NaN since Postgresql allows it.

`decimal` does what I want except that I am trying to use decimal fixed-point numbers, which Scientific affords, not binary floating-point numbers.

If instead of:
```
numeric :: BeamSqlBackend be => Maybe (Word, Maybe Word) -> DataType be Scientific
```
there is:
```
numeric :: BeamSqlBackend be => Maybe (Word, Maybe Word) -> DataType be (Maybe Scientific)
```

Then NaN could be represented as `Nothing` and my immediate problem would be fixed, though +/-Inf would still be problematic.