feat: dockerfile and github based CI build for Africastalking variant (#174)

## Summary

* fixed missing error handler in main
* add injectable build string in main
* add (dynamically linked) docker build
* add github CI workflow
* add extra but useful dev files in dev folder

* closes #93

## Notes

* We'll move to a self-hosted CI runner once it is installed on Gitea.

Reviewed-on: urdt/ussd#174
Co-authored-by: Mohammed Sohail <sohailsameja@gmail.com>
Co-committed-by: Mohammed Sohail <sohailsameja@gmail.com>

cmd/africastalking/main.go

@@ -29,8 +29,10 @@ import (
 )
 
 var (
-	logg        = logging.NewVanilla()
-	scriptDir   = path.Join("services", "registration")
+	logg      = logging.NewVanilla()
+	scriptDir = path.Join("services", "registration")
+
+	build = "dev"
 )
 
 func init() {
@@ -115,7 +117,7 @@ func main() {
 	flag.UintVar(&port, "p", initializers.GetEnvUint("PORT", 7123), "http port")
 	flag.Parse()
 
-	logg.Infof("start command", "dbdir", dbDir, "resourcedir", resourceDir, "outputsize", size)
+	logg.Infof("start command", "build", build, "dbdir", dbDir, "resourcedir", resourceDir, "outputsize", size)
 
 	ctx := context.Background()
 	ctx = context.WithValue(ctx, "Database", database)
@@ -157,6 +159,10 @@ func main() {
 	}
 
 	lhs, err := handlers.NewLocalHandlerService(ctx, pfp, true, dbResource, cfg, rs)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, err.Error())
+		os.Exit(1)
+	}
 	lhs.SetDataStore(&userdataStore)
 
 	if err != nil {