error_url required in the url_sig file

The error_url parameter in the URL signature file is required, if not present trafficserver doesn't start.

Seems like TO handles generating the proper location of for the url_sig in the the database to all servers assigned, although the error_url is not.

• I tried to put the parameter in the DS profile parameter, but it didn't get generated on disk.
• Thinking that a default of `error_url = 403` should be dynamic generated if not present to prevent trafficserver from starting. This could have other implication.
• Other suggestions?