[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>

app/server.go

@@ -170,6 +170,12 @@ type Server struct {
 	CacheProvider cache.Provider
 
 	tracer *tracing.Tracer
+
+	// These are used to prevent concurrent upload requests
+	// for a given upload session which could cause inconsistencies
+	// and data corruption.
+	uploadLockMapMut sync.Mutex
+	uploadLockMap    map[string]bool
 }
 
 func NewServer(options ...Option) (*Server, error) {
@@ -182,6 +188,7 @@ func NewServer(options ...Option) (*Server, error) {
 		LocalRouter:         localRouter,
 		licenseListeners:    map[string]func(*model.License, *model.License){},
 		hashSeed:            maphash.MakeSeed(),
+		uploadLockMap:       map[string]bool{},
 	}
 
 	for _, option := range options {