Piccolo Files

Added the having clause, which is useful when working with group_by.

For example, here we get the number of albums per band, but exclude any bands with less than 2 albums:

:::python
>>> from piccolo.query.functions.aggregate import Count

>>> await Album.select(
...     Album.band.name.as_alias('band_name'),
...     Count()
... ).group_by(
...     Album.band
... ).having(
...     Count() >= 2
... )

[
    {"band_name": "Pythonistas", "count": 2},
]

We also updated our CockroachDB support to the latest version (thanks to @sinisaos for this).