Transforms::Base64: add padding option and docs

lib/moneta/transforms/base64.rb

@@ -1,27 +1,43 @@
-require 'base64'
+require "base64"
 
 module Moneta
   module Transforms
     # Encodes text as Base64 using the stdlib +base64+ library
     class Base64 < Transform
-      def initialize(url_safe: false, strict: false, **options)
+      # @param url_safe [Boolean] If +true+, URL-safe base64 will be used instead.
+      # @param strict [Boolean] By default the resulting string has line breaks in it.  Specifying
+      #   +strict: true+ will remove line breaks.
+      # @param padding [Boolean] This can be set to +false+ in conjuction with +url_safe: true+ to output unpadded
+      #   URL-safe Base64
+      def initialize(url_safe: false, strict: false, padding: true, **options)
         super
 
         raise "Cannot use strict and url_safe together" if url_safe && strict
+        raise "padding: false is only valid with url_safe: true" if !padding && !url_safe
+
         @url_safe = url_safe
         @strict = strict
+        @padding = padding
       end
 
+      # Encode string to Base64
+      #
+      # @param value [String]
+      # @return [String]
       def encode(value)
         if @url_safe
-          ::Base64.urlsafe_encode64(value)
+          ::Base64.urlsafe_encode64(value, padding: @padding)
         elsif @strict
           ::Base64.strict_encode64(value)
         else
           ::Base64.encode64(value)
         end
       end
 
+      # Decode from Base64
+      #
+      # @param value [String]
+      # @return [String]
       def decode(value)
         if @url_safe
           ::Base64.urlsafe_decode64(value)