restructure storage driver

internal/pastes/paste.go

@@ -0,0 +1,9 @@
+package pastes
+
+type Paste struct {
+	ID                string                 `json:"id"`
+	Content           string                 `json:"content"`
+	ModificationToken string                 `json:"modificationToken,omitempty"`
+	Created           int64                  `json:"created"`
+	Metadata          map[string]interface{} `json:"metadata"`
+}

internal/pastes/repository.go

@@ -0,0 +1,14 @@
+package pastes
+
+import (
+	"context"
+	"time"
+)
+
+type Repository interface {
+	ListIDs(ctx context.Context) ([]string, error)
+	FindByID(ctx context.Context, id string) (*Paste, error)
+	Upsert(ctx context.Context, paste *Paste) error
+	DeleteByID(ctx context.Context, id string) error
+	DeleteOlderThan(ctx context.Context, age time.Duration) (int, error)
+}