PluginAPI: add ability to retrieve users by ids (#26936)

* pluginapi: ability to retrieve users by ids

* fix test

server/public/pluginapi/user_test.go

@@ -96,6 +96,35 @@ func TestGetUsers(t *testing.T) {
 	})
 }
 
+func TestListByUserIDs(t *testing.T) {
+	t.Run("success", func(t *testing.T) {
+		api := &plugintest.API{}
+		defer api.AssertExpectations(t)
+		client := pluginapi.NewClient(api, &plugintest.Driver{})
+
+		userIDs := []string{"123"}
+		expectedUsers := []*model.User{{Id: "123", Username: "test"}}
+		api.On("GetUsersByIds", userIDs).Return(expectedUsers, nil)
+
+		actualUsers, err := client.User.ListByUserIDs(userIDs)
+		require.NoError(t, err)
+		assert.Equal(t, expectedUsers, actualUsers)
+	})
+
+	t.Run("failure", func(t *testing.T) {
+		api := &plugintest.API{}
+		defer api.AssertExpectations(t)
+		client := pluginapi.NewClient(api, &plugintest.Driver{})
+
+		userIDs := []string{"123"}
+		api.On("GetUsersByIds", userIDs).Return(nil, newAppError())
+
+		actualUsers, err := client.User.ListByUserIDs(userIDs)
+		require.EqualError(t, err, "here: id, an error occurred")
+		assert.Nil(t, actualUsers)
+	})
+}
+
 func TestGetUser(t *testing.T) {
 	t.Run("success", func(t *testing.T) {
 		api := &plugintest.API{}