Disallow use of non-projection operations in proj (was: Don't convert non-angular inputs to proj to radians) #1162
Thinking more about this, I am having doubts that this is the best solution. I am starting to lean towards
Since the introduction of other operations types than projections it has been unclear how proj should treat those. This commit sets record straight once and for all: proj is only allowed to initialize operations that take angular input and produces non-angular output, i.e. projections. This is true to the version of proj before the introduction of the pipeline and other non-projection operations. Users can still initiliaze pipelines with proj as long as the resulting concatenated operation requires angular input and outputs non-angular output.