Adding database to pipeline

database-pipeline.clj

(defn internal-error
  "Generate an HTTP response map representing an Internal Server Error."
  [body]
  (assoc (response body) :status 500))

(defn post-notes-handler
  "Map an HTTP request to a newly-created note."
  [req-body]
  (let [[note error] (validate-note req-body)]
    (if error
      (bad-request error)
      (let [[id error] (create-note req-body)]
        (if error
          (internal-error error)
          (ok (assoc req-body :id id)))))))