Add a webhook to create messages from Splunk search alerts. The search
alert JSON includes the first search result and a link to view the full
results. The following fields are used:
* search_name - the name of the saved search
* results_link - URL of the full search results
* host - the host the search result came from
* source - the source file on that host
* _raw - the raw text of the logged event.
The Zulip message contains:
* search name
* host
* source
* raw
The destination stream and message topic are configurable: the default
stream is "splunk" and the default topic "Splunk Alert". If the topic is
not provided in the URL, the search name is used instead (truncated if too
long. If a needed field is missing, a default value is used instead.
Example: "Missing source"
It is possible to configure a Splunk search to not include some values,
so I've provided defaults rather than return an error for missing data.
In practice, these fields are unlikely to be deliberately suppressed.
Note: alerts are only available for Splunk servers using a valid trial,
developer, or paid license.
I've added tests for the normal case of one search result, the topic from
the search name, and for a search missing one of the fields used. Tested
using Splunk Enterprise 6.5.1.
Fixes#3477
Feorlen