feat: add COMMENT support to indexes

This reads out any COMMENT added to an INDEX object and adds its after
the last output on its "details" line.

lib/annotate/annotate_models.rb

@@ -36,6 +36,10 @@ module AnnotateModels
  using: {
  default: 'USING',
  markdown: '_using_'
+ },
+ comment: {
+ default: 'COMMENT',
+ markdown: '_comment_'
  }
  }.freeze
 
@@ -295,12 +299,22 @@ def index_using_info(index, format = :default)
  end
  end
 
+ def index_comment_info(index, format = :default)
+ value = index.try(:comment).try(:to_s)
+ if value.blank?
+ ''
+ else
+ " #{INDEX_CLAUSES[:comment][format]} #{value}"
+ end
+ end
+
  def final_index_string_in_markdown(index)
  details = sprintf(
- "%s%s%s",
+ "%s%s%s%s",
  index_unique_info(index, :markdown),
  index_where_info(index, :markdown),
- index_using_info(index, :markdown)
+ index_using_info(index, :markdown),
+ index_comment_info(index, :markdown)
  ).strip
  details = " (#{details})" unless details.blank?
 
@@ -314,12 +328,13 @@ def final_index_string_in_markdown(index)
 
  def final_index_string(index, max_size)
  sprintf(
- "# %-#{max_size}.#{max_size}s %s%s%s%s",
+ "# %-#{max_size}.#{max_size}s %s%s%s%s%s",
  index.name,
  "(#{index_columns_info(index).join(',')})",
  index_unique_info(index),
  index_where_info(index),
- index_using_info(index)
+ index_using_info(index),
+ index_comment_info(index)
  ).rstrip + "\n"
  end