Webhook invocation history only records first 255 characters of request URL and result description

A fix was applied in https://jira.atlassian.com/browse/BSERV-10608 to truncate to 255 chars for data being inserted into two of the columns on the webhook invocation history table (ie the request URL and the result description fields).

This means there is a bit of a mismatch between the webhook definition (which can have URLs with more than 255 chars) and the invocation history.

This bug is about addressing the mismatch, and making the webhook invocation history columns capable of recording the same size of data as the webhook definition itself.