feat: Trivial default quota configuration

This adds a new configuration setting: `[quota.default].TOTAL`, which
will be used if no groups are configured for a particular user. The new
option makes it possible to entirely skip configuring quotas via the API
if all that one wants is a total size.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

modules/setting/quota.go

@@ -7,9 +7,18 @@ package setting
 var Quota = struct {
 	Enabled       bool     `ini:"ENABLED"`
 	DefaultGroups []string `ini:"DEFAULT_GROUPS"`
+
+	Default struct {
+		Total int64
+	} `ini:"quota.default"`
 }{
 	Enabled:       false,
 	DefaultGroups: []string{},
+	Default: struct {
+		Total int64
+	}{
+		Total: -1,
+	},
 }
 
 func loadQuotaFrom(rootCfg ConfigProvider) {