Un/bound methods and proxy method as a symbol for column format

This allows to write something akin to

format: String.instance_method(:to_json)

or

format: :json

class MyTabulatrData < Tabulatr::Data
  ...
  # define_singleton_method(:json) {|x| x&.to_json}
  class << self
    # Formatter for a column
    def json(x)
      x&.to_json
    end
  end
end

lib/tabulatr/renderer/column.rb

@@ -177,7 +177,16 @@ def filter_type_for_integer
 
   def format_value(value, view)
     case self.col_options.format
-    when Symbol then view.send(col_options.format, value)
+    when UnboundMethod then
+      m = col_options.format.bind(value)
+      m.call
+    when Method then col_options.format.call(value)
+    when Symbol then
+      if proxy.respond_to?(col_options.format)
+        proxy.send(col_options.format, value)
+      else
+        view.send(col_options.format, value)
+      end
     when String then col_options.format % value
     when Proc   then col_options.format.(value)
     else value