fix(GODT-2822): Handle 429 during message download

When we run into 429 during a message download, do not cancel the whole
batch and switch to a sequential downloader to avoid API overload.

internal/user/mocks/mocks.go

@@ -0,0 +1,66 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/ProtonMail/proton-bridge/v3/internal/user (interfaces: MessageDownloader)
+
+// Package mocks is a generated GoMock package.
+package mocks
+
+import (
+	context "context"
+	io "io"
+	reflect "reflect"
+
+	proton "github.com/ProtonMail/go-proton-api"
+	gomock "github.com/golang/mock/gomock"
+)
+
+// MockMessageDownloader is a mock of MessageDownloader interface.
+type MockMessageDownloader struct {
+	ctrl     *gomock.Controller
+	recorder *MockMessageDownloaderMockRecorder
+}
+
+// MockMessageDownloaderMockRecorder is the mock recorder for MockMessageDownloader.
+type MockMessageDownloaderMockRecorder struct {
+	mock *MockMessageDownloader
+}
+
+// NewMockMessageDownloader creates a new mock instance.
+func NewMockMessageDownloader(ctrl *gomock.Controller) *MockMessageDownloader {
+	mock := &MockMessageDownloader{ctrl: ctrl}
+	mock.recorder = &MockMessageDownloaderMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockMessageDownloader) EXPECT() *MockMessageDownloaderMockRecorder {
+	return m.recorder
+}
+
+// GetAttachmentInto mocks base method.
+func (m *MockMessageDownloader) GetAttachmentInto(arg0 context.Context, arg1 string, arg2 io.ReaderFrom) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetAttachmentInto", arg0, arg1, arg2)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// GetAttachmentInto indicates an expected call of GetAttachmentInto.
+func (mr *MockMessageDownloaderMockRecorder) GetAttachmentInto(arg0, arg1, arg2 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetAttachmentInto", reflect.TypeOf((*MockMessageDownloader)(nil).GetAttachmentInto), arg0, arg1, arg2)
+}
+
+// GetMessage mocks base method.
+func (m *MockMessageDownloader) GetMessage(arg0 context.Context, arg1 string) (proton.Message, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetMessage", arg0, arg1)
+	ret0, _ := ret[0].(proton.Message)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// GetMessage indicates an expected call of GetMessage.
+func (mr *MockMessageDownloaderMockRecorder) GetMessage(arg0, arg1 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetMessage", reflect.TypeOf((*MockMessageDownloader)(nil).GetMessage), arg0, arg1)
+}