What is the OCNH2 group called?
The group itself unprotonated is called a carboximidate as noted by the Wiki page.  The acid that the group is derived from is carboximidic acid.  As is common practice with imines, the nomenclature for the corresponding protonated halide is done by removing -es, adding -ium, and the halide name.  If this is done using the acid name, the group will be called a carboximinium chloride.