Fix share/space link in notification mail

Use OCIS_URL as the link base. This change also makes sure that the
top-level OcisURL config value gets a default assigned, even when
OCIS_URL is unset.

Fixes: #4688

ocis-pkg/config/defaultconfig.go

@@ -35,6 +35,7 @@ import (
 
 func DefaultConfig() *Config {
 	return &Config{
+		OcisURL: "https://localhost:9200",
 		Runtime: Runtime{
 			Port: "9250",
 			Host: "localhost",

ocis-pkg/config/parser/parse.go

@@ -124,6 +124,10 @@ func EnsureCommons(cfg *config.Config) {
 	if cfg.AdminUserID != "" {
 		cfg.Commons.AdminUserID = cfg.AdminUserID
 	}
+
+	if cfg.OcisURL != "" {
+		cfg.Commons.OcisURL = cfg.OcisURL
+	}
 }
 
 func Validate(cfg *config.Config) error {