WebUI: Possibility to choose object when API call returns list of objects

In case that API call returns array of objects which contains data, using
'object_index' attribute in adapter specification we can set which object
should be used.

It is possible to choose only one object specified by its index in array.

Part of: https://pagure.io/freeipa/issue/6601

Reviewed-By: Petr Vobornik <pvoborni@redhat.com>

install/ui/src/freeipa/field.js

@@ -818,6 +818,15 @@ field.Adapter = declare(null, {
      */
     result_index: 0,
 
+    /**
+     * When result of API call is an array of object this object index
+     * allows to specify exact object in array according to its position.
+     * Default value is null which means do not use object_index.
+     *
+     * @type {Number|null}
+     */
+    object_index: null,
+
     /**
      * Name of the record which we want to extract from the result.
      * Used in dnslocations.
@@ -849,6 +858,10 @@ field.Adapter = declare(null, {
             else if (dr.results) {
                 var result = dr.results[this.result_index];
                 if (result) record = result[this.result_name];
+                var res_type = typeof record;
+                var obj_in_type = typeof this.object_index;
+                if (res_type === 'object' && obj_in_type === 'number')
+                    record = record[this.object_index];
             }
         }
         return record;