Closes#285688
This is misleading because `initialScript` will only be executed at the
*very first* run of postgresql. I.e. when deploying synapse to a server
with an existing postgresql, this won't work.
We don't have a good way of automatically provisioning databases
_declaratively_, so for now just explain what needs to be done here and
leave it to the user how to include this into their deployment.
a3d3cdf5d9