MM-43918: freemium limit for storage (#20225)

Summary
Adds an API end point to return storage usage

Ticket Link
https://mattermost.atlassian.net/browse/MM-43918

store/storetest/file_info_store.go

@@ -29,6 +29,7 @@ func TestFileInfoStore(t *testing.T, ss store.Store) {
 	t.Run("FileInfoPermanentDeleteByUser", func(t *testing.T) { testFileInfoPermanentDeleteByUser(t, ss) })
 	t.Run("GetFilesBatchForIndexing", func(t *testing.T) { testFileInfoStoreGetFilesBatchForIndexing(t, ss) })
 	t.Run("CountAll", func(t *testing.T) { testFileInfoStoreCountAll(t, ss) })
+	t.Run("GetStorageUsage", func(t *testing.T) { testFileInfoGetStorageUsage(t, ss) })
 }
 
 func testFileInfoSaveGet(t *testing.T, ss store.Store) {
@@ -725,3 +726,44 @@ func testFileInfoStoreCountAll(t *testing.T, ss store.Store) {
 	require.NoError(t, err)
 	require.Equal(t, int64(2), count)
 }
+
+func testFileInfoGetStorageUsage(t *testing.T, ss store.Store) {
+	_, err := ss.FileInfo().PermanentDeleteBatch(model.GetMillis(), 100000)
+	require.NoError(t, err)
+	f1, err := ss.FileInfo().Save(&model.FileInfo{
+		PostId:    model.NewId(),
+		CreatorId: model.NewId(),
+		Size:      10,
+		Path:      "file1.txt",
+	})
+	require.NoError(t, err)
+
+	_, err = ss.FileInfo().Save(&model.FileInfo{
+		PostId:    model.NewId(),
+		CreatorId: model.NewId(),
+		Size:      10,
+		Path:      "file2.txt",
+	})
+	require.NoError(t, err)
+	_, err = ss.FileInfo().Save(&model.FileInfo{
+		PostId:    model.NewId(),
+		CreatorId: model.NewId(),
+		Size:      10,
+		Path:      "file3.txt",
+	})
+	require.NoError(t, err)
+
+	usage, err := ss.FileInfo().GetStorageUsage(false, false)
+	require.NoError(t, err)
+	require.Equal(t, int64(30), usage)
+
+	_, err = ss.FileInfo().DeleteForPost(f1.PostId)
+	require.NoError(t, err)
+	usage, err = ss.FileInfo().GetStorageUsage(false, false)
+	require.NoError(t, err)
+	require.Equal(t, int64(20), usage)
+
+	usage, err = ss.FileInfo().GetStorageUsage(false, true)
+	require.NoError(t, err)
+	require.Equal(t, int64(30), usage)
+}

store/storetest/mocks/FileInfoStore.go

@@ -236,6 +236,27 @@ func (_m *FileInfoStore) GetFromMaster(id string) (*model.FileInfo, error) {
 	return r0, r1
 }
 
+// GetStorageUsage provides a mock function with given fields: allowFromCache, includeDeleted
+func (_m *FileInfoStore) GetStorageUsage(allowFromCache bool, includeDeleted bool) (int64, error) {
+	ret := _m.Called(allowFromCache, includeDeleted)
+
+	var r0 int64
+	if rf, ok := ret.Get(0).(func(bool, bool) int64); ok {
+		r0 = rf(allowFromCache, includeDeleted)
+	} else {
+		r0 = ret.Get(0).(int64)
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(bool, bool) error); ok {
+		r1 = rf(allowFromCache, includeDeleted)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // GetWithOptions provides a mock function with given fields: page, perPage, opt
 func (_m *FileInfoStore) GetWithOptions(page int, perPage int, opt *model.GetFileInfosOptions) ([]*model.FileInfo, error) {
 	ret := _m.Called(page, perPage, opt)