implement get likes endpoint.

[WilliamDormer]

This endpoint simply returns the number of likes that a user has, after authentication of course. I'm not 100% sure how we want to do this though, because the likes could be stale (they were sent to a person when their profile was different/had different filters). So you'll have to go through each like they have incoming in the swipe table and verify that it is valid with their profile. This is actually a pretty difficult problem because it brings up the issue of likes being dependent on the state of a person's profile at a given time. Perhaps we need to make a note of when the profile changes in a significant way (ie dating goal changes, gender changes, bodytype changes etc, but not things like bio) and then check if the like has been made before after that update date. Alternatively, we could hash the profile fields that we deem critical and then save that hash with the swipe, and then compare it to the profile when we are returning the number, or getting the valid swipes on a person.
Likes should probably also have an expiry date as well...