add fully_qualify_constant private method

I'm moving a chunk of code out of the constant_name_from_node method.
This makes the intend clearer.

Author: doodzik

lib/packwerk/const_node_inspector.rb

@@ -17,12 +17,7 @@ def constant_name_from_node(node, ancestors:)
       return nil if parent && Node.constant?(parent)
 
       if constant_in_module_or_class_definition?(node, parent: parent)
-        # We're defining a class with this name, in which case the constant is implicitly fully qualified by its
-        # enclosing namespace
-        name = Node.parent_module_name(ancestors: ancestors)
-        name ||= Node.enclosing_namespace_path(node, ancestors: ancestors).push(Node.constant_name(node)).join("::")
-
-        "::" + name
+        fully_qualify_constant(node, ancestors: ancestors)
       else
         begin
           Node.constant_name(node)
@@ -40,5 +35,19 @@ def constant_in_module_or_class_definition?(node, parent:)
         parent_name && parent_name == Node.constant_name(node)
       end
     end
+
+    def fully_qualify_constant(node, ancestors:)
+      # We're defining a class with this name, in which case the constant is implicitly fully qualified by its
+      # enclosing namespace
+      name = Node.parent_module_name(ancestors: ancestors)
+      name ||= generate_qualified_constant(node, ancestors)
+      "::" + name
+    end
+
+    def generate_qualified_constant(node, ancestors:)
+      namespace_path = Node.enclosing_namespace_path(node, ancestors: ancestors)
+      constant_name = Node.constant_name(node)
+      namespace_path.push(constant_name).join("::")
+    end
   end
 end