Export DKIM query functionality

[kbolino]

Please provide an externally usable API to run queries for DKIM records and see the parsed results.

[emersion]

What is your use-case? Why do you need this?

[kbolino]

I'd like to verify that the records have been set up properly for a domain.

[emersion]

Sounds sensible. Need to document explicitly that the function shouldn't be used to check a DKIM signature.