unistore: move continue to the resource package (#101206)

* minor improvements to tests

* move continue token

* update sql backend

pkg/storage/unified/sql/backend.go

@@ -588,11 +588,11 @@ type listIter struct {
 
 // ContinueToken implements resource.ListIterator.
 func (l *listIter) ContinueToken() string {
-	return ContinueToken{ResourceVersion: l.listRV, StartOffset: l.offset}.String()
+	return resource.ContinueToken{ResourceVersion: l.listRV, StartOffset: l.offset}.String()
 }
 
 func (l *listIter) ContinueTokenWithCurrentRV() string {
-	return ContinueToken{ResourceVersion: l.rv, StartOffset: l.offset}.String()
+	return resource.ContinueToken{ResourceVersion: l.rv, StartOffset: l.offset}.String()
 }
 
 func (l *listIter) Error() error {
@@ -679,7 +679,7 @@ func (b *backend) listAtRevision(ctx context.Context, req *resource.ListRequest,
 	// Get the RV
 	iter := &listIter{listRV: req.ResourceVersion}
 	if req.NextPageToken != "" {
-		continueToken, err := GetContinueToken(req.NextPageToken)
+		continueToken, err := resource.GetContinueToken(req.NextPageToken)
 		if err != nil {
 			return 0, fmt.Errorf("get continue token: %w", err)
 		}
@@ -737,7 +737,7 @@ func (b *backend) getHistory(ctx context.Context, req *resource.ListRequest, cb
 
 	iter := &listIter{}
 	if req.NextPageToken != "" {
-		continueToken, err := GetContinueToken(req.NextPageToken)
+		continueToken, err := resource.GetContinueToken(req.NextPageToken)
 		if err != nil {
 			return 0, fmt.Errorf("get continue token: %w", err)
 		}

pkg/storage/unified/sql/continue.go

@@ -1,32 +0,0 @@
-package sql
-
-import (
-	"encoding/base64"
-	"encoding/json"
-	"fmt"
-)
-
-type ContinueToken struct {
-	StartOffset     int64 `json:"o"`
-	ResourceVersion int64 `json:"v"`
-}
-
-func (c ContinueToken) String() string {
-	b, _ := json.Marshal(c)
-	return base64.StdEncoding.EncodeToString(b)
-}
-
-func GetContinueToken(token string) (*ContinueToken, error) {
-	continueVal, err := base64.StdEncoding.DecodeString(token)
-	if err != nil {
-		return nil, fmt.Errorf("error decoding continue token")
-	}
-
-	t := &ContinueToken{}
-	err = json.Unmarshal(continueVal, t)
-	if err != nil {
-		return nil, err
-	}
-
-	return t, nil
-}