swagger-feature ~looks like:

(def swagger-feature
  "Feature for handling swagger-documentation for routes.
  Works both with Middleware & Interceptors. Does not participate
  in actual request processing, just provides specs for the extra
  valid keys for the route data. Should be accompanied by a
  [[swagger-spec-handler]] to expose the swagger spec.

  Swagger-spesific keys:

  | key           | description |
  | --------------|-------------|
  | :swagger      | map of any swagger-data. Must have `:id` to identify the api

  The following common route keys also contribute to swagger spec:

  | key           | description |
  | --------------|-------------|
  | :no-doc       | optional boolean to exclude endpoint from api docs
  | :tags         | optional set of strings of keywords tags for an endpoint api docs
  | :summary      | optional short string summary of an endpoint
  | :description  | optional long description of an endpoint. Supports 
  | :parameters   | optional input parameters for a route, in a format defined by the coercion
  | :responses    | optional descriptions of responess, in a format defined by coercion

  Example:

      [\"/api\"
       {:swagger {:id :my-api}
        :middleware [reitit.swagger/swagger-feature]}

       [\"/swagger.json\"
        {:get {:no-doc true
               :swagger {:info {:title \"my-api\"}}
               :handler reitit.swagger/swagger-spec-handler}}]

       [\"/plus\"
        {:get {:tags #{:math}
               :summary \"adds numbers together\"
               :description \"takes `x` and `y` query-params and adds them together\"
               :parameters {:query {:x int?, :y int?}}
               :responses {200 {:body {:total pos-int?}}}
               :handler (fn [{:keys [parameters]}]
                          {:status 200
                           :body (+ (-> parameters :query :x)
                                    (-> parameters :query :y)})}}]]"
  {:name ::swagger
   :spec ::spec})