[MM-30436] Add support for configuration custom defaults (#16265)

* [MM-30436] Add support for configuration custom defaults

* Addressing review comments

* Addressing PR comments

* Soft fail if the configuration defaults cannot be read

* Directly print error in log message

* Fix linter

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/server.go

@@ -210,7 +210,7 @@ func NewServer(options ...Option) (*Server, error) {
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to load config")
 		}
-		configStore, err := config.NewStoreFromBacking(innerStore)
+		configStore, err := config.NewStoreFromBacking(innerStore, nil)
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to load config")
 		}