Record activations against each alias record

[abiddiscombe]

Add a new feature for logging unique "activations" of each alias record. This should include both lookup (/link) and redirection (/to/:alias) events, but with the ability to distinguish between the two.

• Activation data should be visible to the user on the /link endpoint.
• Data should be stored in a new table within the existing PostgreSQL database.
• Extensions to response times (incurred from writing database records) should be minimal.