[MM-26812] Add support for resumable file uploads (#15252)

* Implement AppendFile for FileBackend

* Split test into subtests

* [MM-26812] Add support for resumable file uploads (#15252)

* Implement UploadSession

* Implement UploadSessionStore

* Add error strings

* Implement resumable file uploads

* Add UploadType

* Fix retry layer tests

* Regenerate store layers

* Fix store error handling

* Use base for filename

* Prevent concurrent uploads on the same upload session

* Fix erroneus error string

* Improve error handling

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

* Fix translations

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/upload_session_test.go

@@ -0,0 +1,125 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUploadSessionIsValid(t *testing.T) {
+	var session UploadSession
+
+	t.Run("empty session should fail", func(t *testing.T) {
+		err := session.IsValid()
+		require.NotNil(t, err)
+	})
+
+	t.Run("valid session should succeed", func(t *testing.T) {
+		session = UploadSession{
+			Id:         NewId(),
+			Type:       UploadTypeAttachment,
+			CreateAt:   GetMillis(),
+			UserId:     NewId(),
+			ChannelId:  NewId(),
+			Filename:   "test",
+			Path:       "/tmp/test",
+			FileSize:   1024,
+			FileOffset: 0,
+		}
+		err := session.IsValid()
+		require.Nil(t, err)
+	})
+
+	t.Run("invalid Id should fail", func(t *testing.T) {
+		us := session
+		us.Id = "invalid"
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.id.app_error", err.Id)
+	})
+
+	t.Run("invalid type should fail", func(t *testing.T) {
+		us := session
+		us.Type = "invalid"
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.type.app_error", err.Id)
+	})
+
+	t.Run("invalid CreateAt should fail", func(t *testing.T) {
+		us := session
+		us.CreateAt = 0
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.create_at.app_error", err.Id)
+	})
+
+	t.Run("invalid UserId should fail", func(t *testing.T) {
+		us := session
+		us.UserId = "invalid"
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.user_id.app_error", err.Id)
+	})
+
+	t.Run("invalid ChannelId should fail", func(t *testing.T) {
+		us := session
+		us.ChannelId = "invalid"
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.channel_id.app_error", err.Id)
+	})
+
+	t.Run("ChannelId is not validated if type is not attachment", func(t *testing.T) {
+		us := session
+		us.ChannelId = ""
+		us.Type = UploadTypeImport
+		err := us.IsValid()
+		require.Nil(t, err)
+	})
+
+	t.Run("invalid Filename should fail", func(t *testing.T) {
+		us := session
+		us.Filename = ""
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.filename.app_error", err.Id)
+	})
+
+	t.Run("invalid Path should fail", func(t *testing.T) {
+		us := session
+		us.Path = ""
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.path.app_error", err.Id)
+	})
+
+	t.Run("invalid FileSize should fail", func(t *testing.T) {
+		us := session
+		us.FileSize = 0
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.file_size.app_error", err.Id)
+
+		us.FileSize = -1
+		err = us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.file_size.app_error", err.Id)
+	})
+
+	t.Run("invalid FileOffset should fail", func(t *testing.T) {
+		us := session
+		us.FileOffset = us.FileSize + 1
+		err := us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.file_offset.app_error", err.Id)
+
+		us.FileOffset = -1
+		err = us.IsValid()
+		require.NotNil(t, err)
+		require.Equal(t, "model.upload_session.is_valid.file_offset.app_error", err.Id)
+	})
+}