add function to handle missing delimiter in regex

modules/swagger-codegen/src/main/java/io/swagger/codegen/DefaultCodegen.java

@@ -542,7 +542,7 @@ public class DefaultCodegen {
      * @return properly-escaped pattern
      */
     public String toRegularExpression(String pattern) {
-        return escapeText(pattern);
+        return escapeText(addRegularExpressionDelimiter(pattern));
     }
 
     /**
@@ -3264,4 +3264,19 @@ public class DefaultCodegen {
             }
         }
     }
+
+    /**
+     * If the pattern misses the delimiter, add "/" to the beginning and end
+     * Otherwise, return the original pattern
+     *
+     * @param pattern the pattern (regular expression)
+     * @return the pattern with delimiter
+     */
+    public String addRegularExpressionDelimiter(String pattern) {
+        if (pattern != null && !pattern.matches("^/.*")) {
+            return "/" + pattern + "/";
+        }
+
+        return pattern;
+    }
 }

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/RubyClientCodegen.java

@@ -727,4 +727,5 @@ public class RubyClientCodegen extends DefaultCodegen implements CodegenConfig {
     public String escapeUnsafeCharacters(String input) {
         return input.replace("=end", "=_end").replace("=begin", "=_begin");
     }
+
 }