BIND 10 #2213: revise LoadZoneCommand::exec() of b10-auth to use the configurator thread

[BIND 10 Development]

#2213: revise LoadZoneCommand::exec() of b10-auth to use the configurator thread
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                   Reporter:         |                 Owner:  jinmei
  jinmei                             |                Status:  reviewing
                       Type:  task   |             Milestone:
                   Priority:         |  Sprint-20121106
  medium                             |            Resolution:
                  Component:         |             Sensitive:  0
  b10-auth                           |           Sub-Project:  DNS
                   Keywords:         |  Estimated Difficulty:  4
            Defect Severity:  N/A    |           Total Hours:  0
Feature Depending on Ticket:         |
  background zone loading            |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 Some important points first:

 Since this version doesn't validate name or class beyond they are
 string, it causes unexpected termination of builder due to bogus name
 or class value (such as "example..com", or "INN").  At least this
 should be fixed some way.

 One way is to tighten the validation in the builder, but I personally
 think it's better to catch it at the manager side because we can then
 give the user (if it comes from a user via bindctl etc) an immediate
 error report.

 As for hardcoding as an intermediate workaround, I'm okay with it, but
 I'd suggest leaving some comments about this point.

 And, a relatively minor points:

 - maybe we should generalize `LoadZoneCommandError` so we can use it
   for all commands (in case we want to throw an error from them).
 - why do we need `AuthSrv::loadZone`?  I guess `LoadZoneCommand` can
   do `server.getDataSrcClientsMgr().loadZone()`.

 BTW, I think we need a changelog entry (for the entire feature),
 either as a separate one or by updating changelog no. 495.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2213#comment:9>
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