[MM-55096] Introduce generic StoreResult (#25086)

server/channels/store/store.go

@@ -15,6 +15,7 @@ import (
 	"github.com/mattermost/mattermost/server/v8/channels/product"
 )
 
+// Deprecated: Use GenericStoreResult instead.
 type StoreResult struct {
 	Data any
 
@@ -22,6 +23,15 @@ type StoreResult struct {
 	NErr error
 }
 
+// GenericStoreResult is a type safe version of StoreResult.
+// Once all the code is migrated to use GenericStoreResult, it should be renamed to StoreResult.
+type GenericStoreResult[T any] struct {
+	Data T
+
+	// NErr a temporary field used by the new code for the AppError migration. This will later become Err when the entire store is migrated.
+	NErr error
+}
+
 type Store interface {
 	Team() TeamStore
 	Channel() ChannelStore