Fix check for options and add test

Relates to dakrone@47a7762#r27529460

Author: dakrone

src/clj_http/client.clj

@@ -882,8 +882,8 @@
 
 (defn- nested-keys-to-flatten
   [{:keys [flatten-nested-keys] :as req}]
-  (when (and (not (nil? (opt req :ignore-nested-query-string)))
-             (not (nil? (opt req :flatten-nested-form-params)))
+  (when (and (or (not (nil? (opt req :ignore-nested-query-string)))
+                 (not (nil? (opt req :flatten-nested-form-params))))
              flatten-nested-keys)
     (throw (IllegalArgumentException.
             (str "only :flatten-nested-keys or :ignore-nested-query-string/"

test/clj_http/test/client_test.clj

@@ -1312,6 +1312,16 @@
      {:flatten-nested-form-params true
       :ignore-nested-query-string true
       :flatten-nested-keys [:thing :bar]})
+    (is false "should have thrown exception")
+    (catch IllegalArgumentException e
+      (is (= (.getMessage e)
+             (str "only :flatten-nested-keys or :ignore-nested-query-string/"
+                  ":flatten-nested-keys may be specified, not both")))))
+  (try
+    ((client/wrap-flatten-nested-params identity)
+     {:ignore-nested-query-string true
+      :flatten-nested-keys [:thing :bar]})
+    (is false "should have thrown exception")
     (catch IllegalArgumentException e
       (is (= (.getMessage e)
              (str "only :flatten-nested-keys or :ignore-nested-query-string/"