Pass class name to Sequel::MassAssignmentRestriction error

If the instance has a class name, pass this name to the error
message to better understand the error in monitoring systems such as Sentry.

lib/sequel/model/base.rb

@@ -2035,15 +2035,20 @@ def set_restricted(hash, type)
           if meths.include?(m)
             set_column_value(m, v)
           elsif strict
+            err_msg = -> (msg) do
+              msg << " for class #{self.class.name}" if self.class.name
+              msg
+            end
+
             # Avoid using respond_to? or creating symbols from user input
             if public_methods.map(&:to_s).include?(m)
               if Array(model.primary_key).map(&:to_s).member?(k.to_s) && model.restrict_primary_key?
-                raise MassAssignmentRestriction, "#{k} is a restricted primary key"
+                raise MassAssignmentRestriction, err_msg.call("#{k} is a restricted primary key")
               else
-                raise MassAssignmentRestriction, "#{k} is a restricted column"
+                raise MassAssignmentRestriction, err_msg.call("#{k} is a restricted column")
               end
             else
-              raise MassAssignmentRestriction, "method #{m} doesn't exist"
+              raise MassAssignmentRestriction, err_msg.call("method #{m} doesn't exist")
             end
           end
         end

spec/extensions/csv_serializer_spec.rb

@@ -163,7 +163,8 @@ def self.name; 'Album' end
 
   it "should raise an error if attempting to set a restricted column and :all_columns is not used" do
     @Artist.restrict_primary_key
-    proc{@Artist.from_csv(@artist.to_csv)}.must_raise(Sequel::MassAssignmentRestriction)
+    err = proc{@Artist.from_csv(@artist.to_csv)}.must_raise(Sequel::MassAssignmentRestriction)
+    err.message.must_equal("id is a restricted primary key for class Artist")
   end
 
   it "should use a dataset's selected columns" do

spec/model/base_spec.rb

@@ -664,13 +664,27 @@ class ModelTest2 < Sequel::Model(@db[:foo])
   end
 
   it "should raise an error if a missing/restricted column/method is accessed" do
-    proc{@c.new(:a=>1)}.must_raise(Sequel::MassAssignmentRestriction)
+    err = proc{@c.new(:a=>1)}.must_raise(Sequel::MassAssignmentRestriction)
+    err.message.must_equal("method a= doesn't exist")
     proc{@c.create(:a=>1)}.must_raise(Sequel::MassAssignmentRestriction)
     c = @c.new
     proc{c.set(:a=>1)}.must_raise(Sequel::MassAssignmentRestriction)
     proc{c.update(:a=>1)}.must_raise(Sequel::MassAssignmentRestriction)
   end
 
+  it "should add class name to error message" do
+    item = Class.new(Sequel::Model(:items)) do
+      columns :id
+    end
+
+    item.class_eval do
+      def self.name; 'Item' end
+    end
+
+    err = proc{item.new(:a=>1)}.must_raise(Sequel::MassAssignmentRestriction)
+    err.message.must_equal("method a= doesn't exist for class Item")
+  end
+
   it "should be disabled by strict_param_setting = false" do
     @c.strict_param_setting = false
     @c.strict_param_setting.must_equal false