add key/value store service (#36868)

* add key/value store service

* don't export kvStoreSQL, consumers should interact with KVStore & NamespacedKVStore

* add del method, avoid ErrNotFound (#38627)

* switch value column to medium text

Co-authored-by: Alexander Emelin <frvzmb@gmail.com>

pkg/infra/kvstore/kvstore.go

@@ -0,0 +1,50 @@
+package kvstore
+
+import (
+	"context"
+
+	"github.com/grafana/grafana/pkg/infra/log"
+	"github.com/grafana/grafana/pkg/services/sqlstore"
+)
+
+func ProvideService(sqlStore *sqlstore.SQLStore) KVStore {
+	return &kvStoreSQL{
+		sqlStore: sqlStore,
+		log:      log.New("infra.kvstore.sql"),
+	}
+}
+
+// KVStore is an interface for k/v store.
+type KVStore interface {
+	Get(ctx context.Context, orgId int64, namespace string, key string) (string, bool, error)
+	Set(ctx context.Context, orgId int64, namespace string, key string, value string) error
+	Del(ctx context.Context, orgId int64, namespace string, key string) error
+}
+
+// WithNamespace returns a kvstore wrapper with fixed orgId and namespace.
+func WithNamespace(kv KVStore, orgId int64, namespace string) *NamespacedKVStore {
+	return &NamespacedKVStore{
+		kvStore:   kv,
+		orgId:     orgId,
+		namespace: namespace,
+	}
+}
+
+// NamespacedKVStore is a KVStore wrapper with fixed orgId and namespace.
+type NamespacedKVStore struct {
+	kvStore   KVStore
+	orgId     int64
+	namespace string
+}
+
+func (kv *NamespacedKVStore) Get(ctx context.Context, key string) (string, bool, error) {
+	return kv.kvStore.Get(ctx, kv.orgId, kv.namespace, key)
+}
+
+func (kv *NamespacedKVStore) Set(ctx context.Context, key string, value string) error {
+	return kv.kvStore.Set(ctx, kv.orgId, kv.namespace, key, value)
+}
+
+func (kv *NamespacedKVStore) Del(ctx context.Context, key string) error {
+	return kv.kvStore.Del(ctx, kv.orgId, kv.namespace, key)
+}