First attempt at ripping out agnostic code into ifcopenshell.api namespace. See #1399.

src/ifcopenshell-python/ifcopenshell/api/root/create_product.py

@@ -0,0 +1,31 @@
+import ifcopenshell
+from ifcopenshell.api.owner.api import create_owner_history
+
+
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {
+            "ifc_class": "IfcBuildingElementProxy",
+            "predefined_type": None,
+            "name": None,
+        }
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        element = self.file.create_entity(self.settings["ifc_class"], **{
+            "GlobalId": ifcopenshell.guid.new(),
+            "OwnerHistory": create_owner_history()
+        })
+        element.Name = self.settings["name"] or None
+        if self.settings["predefined_type"]:
+            if hasattr(element, "PredefinedType"):
+                try:
+                    element.PredefinedType = self.settings["predefined_type"]
+                except:
+                    element.PredefinedType = "USERDEFINED"
+                    element.ObjectType = self.settings["predefined_type"]
+            elif hasattr(element, "ObjectType"):
+                element.ObjectType = self.settings["predefined_type"]
+        return element