[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/storetest/mocks/SqlStore.go

@@ -845,6 +845,22 @@ func (_m *SqlStore) UnlockFromMaster() {
 	_m.Called()
 }
 
+// UploadSession provides a mock function with given fields:
+func (_m *SqlStore) UploadSession() store.UploadSessionStore {
+	ret := _m.Called()
+
+	var r0 store.UploadSessionStore
+	if rf, ok := ret.Get(0).(func() store.UploadSessionStore); ok {
+		r0 = rf()
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.UploadSessionStore)
+		}
+	}
+
+	return r0
+}
+
 // User provides a mock function with given fields:
 func (_m *SqlStore) User() store.UserStore {
 	ret := _m.Called()

store/storetest/mocks/Store.go

@@ -596,6 +596,22 @@ func (_m *Store) UnlockFromMaster() {
 	_m.Called()
 }
 
+// UploadSession provides a mock function with given fields:
+func (_m *Store) UploadSession() store.UploadSessionStore {
+	ret := _m.Called()
+
+	var r0 store.UploadSessionStore
+	if rf, ok := ret.Get(0).(func() store.UploadSessionStore); ok {
+		r0 = rf()
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.UploadSessionStore)
+		}
+	}
+
+	return r0
+}
+
 // User provides a mock function with given fields:
 func (_m *Store) User() store.UserStore {
 	ret := _m.Called()

store/storetest/mocks/UploadSessionStore.go

@@ -0,0 +1,112 @@
+// Code generated by mockery v1.0.0. DO NOT EDIT.
+
+// Regenerate this file using `make store-mocks`.
+
+package mocks
+
+import (
+	model "github.com/mattermost/mattermost-server/v5/model"
+	mock "github.com/stretchr/testify/mock"
+)
+
+// UploadSessionStore is an autogenerated mock type for the UploadSessionStore type
+type UploadSessionStore struct {
+	mock.Mock
+}
+
+// Delete provides a mock function with given fields: id
+func (_m *UploadSessionStore) Delete(id string) error {
+	ret := _m.Called(id)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(string) error); ok {
+		r0 = rf(id)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// Get provides a mock function with given fields: id
+func (_m *UploadSessionStore) Get(id string) (*model.UploadSession, error) {
+	ret := _m.Called(id)
+
+	var r0 *model.UploadSession
+	if rf, ok := ret.Get(0).(func(string) *model.UploadSession); ok {
+		r0 = rf(id)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.UploadSession)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(string) error); ok {
+		r1 = rf(id)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// GetForUser provides a mock function with given fields: userId
+func (_m *UploadSessionStore) GetForUser(userId string) ([]*model.UploadSession, error) {
+	ret := _m.Called(userId)
+
+	var r0 []*model.UploadSession
+	if rf, ok := ret.Get(0).(func(string) []*model.UploadSession); ok {
+		r0 = rf(userId)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.UploadSession)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(string) error); ok {
+		r1 = rf(userId)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// Save provides a mock function with given fields: session
+func (_m *UploadSessionStore) Save(session *model.UploadSession) (*model.UploadSession, error) {
+	ret := _m.Called(session)
+
+	var r0 *model.UploadSession
+	if rf, ok := ret.Get(0).(func(*model.UploadSession) *model.UploadSession); ok {
+		r0 = rf(session)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.UploadSession)
+		}
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(*model.UploadSession) error); ok {
+		r1 = rf(session)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// Update provides a mock function with given fields: session
+func (_m *UploadSessionStore) Update(session *model.UploadSession) error {
+	ret := _m.Called(session)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(*model.UploadSession) error); ok {
+		r0 = rf(session)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}