Add a validation of dimension POST for human_readable_field_id

If we have an external remapping, human_readable_field_id is
required. We now return a 400 if that is missing.

src/metabase/api/field.clj

@@ -103,16 +103,20 @@
    dimension-name         su/NonBlankString
    human_readable_field_id (s/maybe su/IntGreaterThanZero)}
   (let [field (api/read-check Field id)]
+    (api/check (or (= dimension-type "internal")
+                   (and (= dimension-type "external")
+                        human_readable_field_id))
+      [400 "Foreign key based remappings require a human readable field id"])
     (if-let [dimension (Dimension :field_id id)]
       (db/update! Dimension (:id dimension)
         {:type dimension-type
          :name dimension-name
          :human_readable_field_id human_readable_field_id})
       (db/insert! Dimension
-                  {:field_id id
-                   :type dimension-type
-                   :name dimension-name
-                   :human_readable_field_id human_readable_field_id}))
+        {:field_id id
+         :type dimension-type
+         :name dimension-name
+         :human_readable_field_id human_readable_field_id}))
     (Dimension :field_id id)))
 
 (api/defendpoint DELETE "/:id/dimension"

test/metabase/api/field_test.clj

@@ -314,6 +314,12 @@
       [before-creation
        (tu/boolean-ids-and-timestamps new-dim)])))
 
+;; External remappings require a human readable field id
+(expect
+  clojure.lang.ExceptionInfo
+  (tt/with-temp* [Field [{field-id-1 :id} {:name "Field Test 1"}]]
+    (dimension-post field-id-1 {:name "some dimension name", :type "external"})))
+
 ;; Ensure we can delete a dimension
 (expect
   [{:id true