[MM-13747] Add ability to list users to plugin API (#10102)

* add GetUsers in plugin api

* change GetUsers(page int, perPage int) ([]*model.User, *model.AppError) to GetUsers(options *model.UserGetOptions) ([]*model.User, *model.AppError)

* Update GetUsers doc

Co-Authored-By: dom3k <szeptweb@gmail.com>

* Update doc in plugin/api.go

Co-Authored-By: dom3k <szeptweb@gmail.com>

* correct database initialization for the test

* Update plugin/api.go

Co-Authored-By: dom3k <szeptweb@gmail.com>

app/plugin_api.go

@@ -179,6 +179,10 @@ func (api *PluginAPI) DeleteUser(userId string) *model.AppError {
 	return err
 }
 
+func (api *PluginAPI) GetUsers(options *model.UserGetOptions) ([]*model.User, *model.AppError) {
+	return api.app.GetUsers(options)
+}
+
 func (api *PluginAPI) GetUser(userId string) (*model.User, *model.AppError) {
 	return api.app.GetUser(userId)
 }

app/plugin_api_test.go

@@ -47,6 +47,93 @@ func setupPluginApiTest(t *testing.T, pluginCode string, pluginManifest string,
 	app.SetPluginsEnvironment(env)
 }
 
+func TestPluginAPIGetUsers(t *testing.T) {
+	th := Setup()
+	defer th.TearDown()
+	api := th.SetupPluginAPI()
+
+	user1, err := th.App.CreateUser(&model.User{
+		Email:    strings.ToLower(model.NewId()) + "success+test@example.com",
+		Password: "password",
+		Username: "user1" + model.NewId(),
+	})
+	require.Nil(t, err)
+	defer th.App.PermanentDeleteUser(user1)
+
+	user2, err := th.App.CreateUser(&model.User{
+		Email:    strings.ToLower(model.NewId()) + "success+test@example.com",
+		Password: "password",
+		Username: "user2" + model.NewId(),
+	})
+	require.Nil(t, err)
+	defer th.App.PermanentDeleteUser(user2)
+
+	user3, err := th.App.CreateUser(&model.User{
+		Email:    strings.ToLower(model.NewId()) + "success+test@example.com",
+		Password: "password",
+		Username: "user3" + model.NewId(),
+	})
+	require.Nil(t, err)
+	defer th.App.PermanentDeleteUser(user3)
+
+	user4, err := th.App.CreateUser(&model.User{
+		Email:    strings.ToLower(model.NewId()) + "success+test@example.com",
+		Password: "password",
+		Username: "user4" + model.NewId(),
+	})
+	require.Nil(t, err)
+	defer th.App.PermanentDeleteUser(user4)
+
+	testCases := []struct {
+		Description   string
+		Page          int
+		PerPage       int
+		ExpectedUsers []*model.User
+	}{
+		{
+			"page 0, perPage 0",
+			0,
+			0,
+			[]*model.User{},
+		},
+		{
+			"page 0, perPage 10",
+			0,
+			10,
+			[]*model.User{user1, user2, user3, user4},
+		},
+		{
+			"page 0, perPage 2",
+			0,
+			2,
+			[]*model.User{user1, user2},
+		},
+		{
+			"page 1, perPage 2",
+			1,
+			2,
+			[]*model.User{user3, user4},
+		},
+		{
+			"page 10, perPage 10",
+			10,
+			10,
+			[]*model.User{},
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.Description, func(t *testing.T) {
+			users, err := api.GetUsers(&model.UserGetOptions{
+				Page:    testCase.Page,
+				PerPage: testCase.PerPage,
+			})
+			assert.Nil(t, err)
+			assert.Equal(t, testCase.ExpectedUsers, users)
+		})
+	}
+}
+
 func TestPluginAPIGetUsersInTeam(t *testing.T) {
 	th := Setup().InitBasic()
 	defer th.TearDown()