Support custom fields on tickets

[Sarah-E-Greene]

At present, you can search by custom-generated fields:

query = @rt.search(:query => %('CF.{Category}' = "Problem"), :verbose => true)

Unfortunately, they aren't shown using ticket_show, and you can't create or update them either. http://requesttracker.wikia.com/wiki/REST says that they should be available during a ticket create.

[rebyn]

I think custom fields are supported:

> rt_client.ticket_update('655644', {'CF-serviceid' => 'sample_serviceid'})
{
                 "Cc" => [],
            "Subject" => "Some Subject",
                 "id" => "655644",
              "Queue" => "support",
              "Owner" => "someone",
            "Creator" => "someone@gmail.com",
           ...
}

When I tried to update a non-existent custom field, it returns error:

> rt_client.ticket_update('655644', {'CF-sefrviceid' => 'some_id'})
UnhandledResponse: # cf-sefrviceid: Unknown field.

id: ticket/655644
CF-sefrviceid: 2 - Degraded

However, this doesn't update the ticket in RT. #bug :(