Allow creation of DNS record when adding a client

### Problem Description
When not using AGH as the DHCP server, if you want your hosts to display in the UI instead of an IP, you have to manually define client name to IP mappings. Now if you want to be able to also resolve those clients across the network, you now have to go over and create a rewrite rule entry.

### Proposed Solution
I'm proposing that tab area of the Client settings be extended to include a new section that allows creation of a DNS record.


* checkbox to enable
* a new field for the FQDN (since the client name may be just the host for readability).

The result would be a new DNS rewrite rule that is created and kept in sync with any changes made to the client entry. The API should also be extended to support these new config options.

### Alternatives Considered
The alternative is to manually create both and risk them being "out of sync" after changes.

### Additional Information