[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>

store/sqlstore/store.go

@@ -92,6 +92,7 @@ type SqlStore interface {
 	Emoji() store.EmojiStore
 	Status() store.StatusStore
 	FileInfo() store.FileInfoStore
+	UploadSession() store.UploadSessionStore
 	Reaction() store.ReactionStore
 	Job() store.JobStore
 	Plugin() store.PluginStore