working settings update.

Settings are loaded from the DB and added to the AppConfig during startup.
When updating settings, they are stored in AppConfig, and written do  the database.

webapp/backend/pkg/config/interface.go

@@ -12,12 +12,16 @@ type Interface interface {
 	WriteConfig() error
 	Set(key string, value interface{})
 	SetDefault(key string, value interface{})
+	MergeConfigMap(cfg map[string]interface{}) error
 
 	AllSettings() map[string]interface{}
+	AllKeys() []string
+	SubKeys(key string) []string
 	IsSet(key string) bool
 	Get(key string) interface{}
 	GetBool(key string) bool
 	GetInt(key string) int
+	GetInt64(key string) int64
 	GetString(key string) string
 	GetStringSlice(key string) []string
 	UnmarshalKey(key string, rawVal interface{}, decoderOpts ...viper.DecoderConfigOption) error