Fix the default external app urls

They were hardcoded to localhost:9200 instead of using the server url
config.

pkg/service/v0/service.go

@@ -72,11 +72,11 @@ func (p Phoenix) getPayload() (payload []byte, err error) {
 			p.config.Phoenix.Config.ExternalApps = []config.ExternalApp{
 				{
 					ID:   "accounts",
-					Path: "https://localhost:9200/accounts.js",
+					Path: singleJoiningSlash(p.config.Phoenix.Config.Server, "accounts.js"),
 				},
 				{
 					ID:   "settings",
-					Path: "https://localhost:9200/settings.js",
+					Path: singleJoiningSlash(p.config.Phoenix.Config.Server, "settings.js"),
 				},
 			}
 		}
@@ -109,6 +109,18 @@ func (p Phoenix) getPayload() (payload []byte, err error) {
 	return
 }
 
+func singleJoiningSlash(a, b string) string {
+	aslash := strings.HasSuffix(a, "/")
+	bslash := strings.HasPrefix(b, "/")
+	switch {
+	case aslash && bslash:
+		return a + b[1:]
+	case !aslash && !bslash:
+		return a + "/" + b
+	}
+	return a + b
+}
+
 // Config implements the Service interface.
 func (p Phoenix) Config(w http.ResponseWriter, r *http.Request) {