FEATURE: Improve errors when title is invalid (#11149)

It used to simply say "title is invalid" without giving any hint what
the problem could be. This commit adds different errors messages for
all caps titles, low entropy titles or titles with very long words.

lib/text_sentinel.rb

@@ -54,12 +54,6 @@ class TextSentinel
     seems_quiet?
   end
 
-  private
-
-  def symbols_regex
-    /[\ -\/\[-\`\:-\@\{-\~]/m
-  end
-
   def seems_meaningful?
     # Minimum entropy if entropy check required
     @opts[:min_entropy].blank? || (entropy >= @opts[:min_entropy])
@@ -71,10 +65,6 @@ class TextSentinel
     @text.gsub(symbols_regex, '').size > 0
   end
 
-  def skipped_locale
-    %w(zh_CN zh_TW ko ja).freeze
-  end
-
   def seems_unpretentious?
     return true if skipped_locale.include?(SiteSetting.default_locale)
     # Don't allow super long words if there is a word length maximum
@@ -87,4 +77,14 @@ class TextSentinel
     SiteSetting.allow_uppercase_posts || @text == @text.mb_chars.downcase.to_s || @text != @text.mb_chars.upcase.to_s
   end
 
+  private
+
+  def symbols_regex
+    /[\ -\/\[-\`\:-\@\{-\~]/m
+  end
+
+  def skipped_locale
+    %w(zh_CN zh_TW ko ja).freeze
+  end
+
 end