True if two or more elements of route are identical

Recursively merges maps. Stolen from https://dnaeon.github.io/recursively-merging-maps-in-clojure/

Construct a filter which, when applied to a list of maps, will pass those which match these targets, where each target is a tuple [key value].

Return the value of this key k in this map m, or this dflt value if there is none.