Application: Make error-template title configurable (#40310)

* Fix error-template title

as in index-template.html

* Test: fix for AppTitle

Co-authored-by: Hugo Häggmark <hugo.haggmark@gmail.com>

pkg/middleware/recovery.go

@@ -133,10 +133,11 @@ func Recovery(cfg *setting.Cfg) web.Handler {
 
 				data := struct {
 					Title     string
+					AppTitle  string
 					AppSubUrl string
 					Theme     string
 					ErrorMsg  string
-				}{"Server Error", cfg.AppSubURL, cfg.DefaultTheme, ""}
+				}{"Server Error", "Grafana", cfg.AppSubURL, cfg.DefaultTheme, ""}
 
 				if setting.Env == setting.Dev {
 					if err, ok := r.(error); ok {