drive: allow setting metadata to fail if failok flag is set

For example using

    --drive-metadata-permissions read,write,failok

Will allow metadata to be read and written but if the writing fails,
then only an ERROR will be written in the log and the transfer won't
fail.

backend/drive/drive.go

@@ -151,6 +151,7 @@ func (rwChoices) Choices() []fs.BitsChoicesInfo {
 		{Bit: uint64(rwOff), Name: "off"},
 		{Bit: uint64(rwRead), Name: "read"},
 		{Bit: uint64(rwWrite), Name: "write"},
+		{Bit: uint64(rwFailOK), Name: "failok"},
 	}
 }
 
@@ -160,6 +161,7 @@ type rwChoice = fs.Bits[rwChoices]
 const (
 	rwRead rwChoice = 1 << iota
 	rwWrite
+	rwFailOK
 	rwOff rwChoice = 0
 )
 
@@ -173,6 +175,9 @@ var rwExamples = fs.OptionExamples{{
 }, {
 	Value: rwWrite.String(),
 	Help:  "Write the value only",
+}, {
+	Value: rwFailOK.String(),
+	Help:  "If writing fails log errors only, don't fail the transfer",
 }, {
 	Value: (rwRead | rwWrite).String(),
 	Help:  "Read and Write the value.",

backend/drive/metadata.go

@@ -262,7 +262,7 @@ func (f *Fs) setLabels(ctx context.Context, info *drive.File, labels []*drive.La
 		return f.shouldRetry(ctx, err)
 	})
 	if err != nil {
-		return fmt.Errorf("failed to set owner: %w", err)
+		return fmt.Errorf("failed to set labels: %w", err)
 	}
 	return nil
 }
@@ -553,7 +553,12 @@ func (f *Fs) updateMetadata(ctx context.Context, updateInfo *drive.File, meta fs
 			}
 			// Can't set Owner on upload so need to set afterwards
 			callbackFns = append(callbackFns, func(ctx context.Context, info *drive.File) error {
-				return f.setOwner(ctx, info, v)
+				err := f.setOwner(ctx, info, v)
+				if err != nil && f.opt.MetadataOwner.IsSet(rwFailOK) {
+					fs.Errorf(f, "Ignoring error as failok is set: %v", err)
+					return nil
+				}
+				return err
 			})
 		case "permissions":
 			if !f.opt.MetadataPermissions.IsSet(rwWrite) {
@@ -566,7 +571,13 @@ func (f *Fs) updateMetadata(ctx context.Context, updateInfo *drive.File, meta fs
 			}
 			// Can't set Permissions on upload so need to set afterwards
 			callbackFns = append(callbackFns, func(ctx context.Context, info *drive.File) error {
-				return f.setPermissions(ctx, info, perms)
+				err := f.setPermissions(ctx, info, perms)
+				if err != nil && f.opt.MetadataPermissions.IsSet(rwFailOK) {
+					// We've already logged the permissions errors individually here
+					fs.Debugf(f, "Ignoring error as failok is set: %v", err)
+					return nil
+				}
+				return err
 			})
 		case "labels":
 			if !f.opt.MetadataLabels.IsSet(rwWrite) {
@@ -579,7 +590,12 @@ func (f *Fs) updateMetadata(ctx context.Context, updateInfo *drive.File, meta fs
 			}
 			// Can't set Labels on upload so need to set afterwards
 			callbackFns = append(callbackFns, func(ctx context.Context, info *drive.File) error {
-				return f.setLabels(ctx, info, labels)
+				err := f.setLabels(ctx, info, labels)
+				if err != nil && f.opt.MetadataLabels.IsSet(rwFailOK) {
+					fs.Errorf(f, "Ignoring error as failok is set: %v", err)
+					return nil
+				}
+				return err
 			})
 		case "folder-color-rgb":
 			updateInfo.FolderColorRgb = v