We now have a representation of correlation functions for correlated noise (see #297). For a noise field with known correlation function, we want to be able to add noise that will whiten the resultant combination - i.e. result in a random field with equal power in each mode.
This is the issue for doing that.
We also want to support convolving correlation functions with PSFs represented by
GSObject instances. This in practice means a double convolution, so needs an additional method. This issue will do that to, along with picking up any minor improvements to the correlation code that I can spot along the way (e.g. maybe speeding up the FFTs by using the SBProfile internals)...