Update data fetcher constructor

[rmarianski]

@zerebubuth, @iandees could you review please?

@iandees I'm assuming that it's ok for the minimum and maximum values to be the same for tileserver.

[iandees]

Hmm, it might not be a good idea to set the max connections to be the same as min. Let me look a little closer 🔍 .

[iandees]

I might be off-by-one here, but I think if we set min and max to the same thing, we won't be able to request all N connections because of this pair of lines: https://github.com/psycopg/psycopg2/blob/master/lib/pool.py#L90-L91

[rmarianski]

It still looks like we'd be ok to me because that branch will only get triggered if there's nothing in self._pool, which will have the minimum number of connections in it.

I deployed this branch to dev so we can wait to see if we get any errors in tileserver related to this after some usage.

[iandees]

Yep, you're right. I think we're OK here.