Description: This function prepares the Subject to be inserted into JSON document by escaping the characters in the String using Json String rules. The function correctly escapes quotes and control-chars (tab, backslash, cr, ff, etc.)

Subject Type: String

Arguments: No arguments

Return Type: String

Examples: If the "message" attribute is 'He didn't say, "Stop!"', then the Expression ${message:escapeJson()} will return 'He didn't say, \"Stop!\"'