Renamed collector, aggregator to api server, api folder to agent (#133)

* Renamed aggregator -> apiServer.

* Format errors with container names.

* Renamed collector -> apiServer.

* Rephrased help messages.

* Moved api -> agent.

* Continue renameing api -> agent in Makefile and Dockerfiles.

agent/pkg/validation/validation.go

@@ -0,0 +1,35 @@
+package validation
+
+import (
+	"fmt"
+	"github.com/go-playground/locales/en"
+	ut "github.com/go-playground/universal-translator"
+	"github.com/go-playground/validator/v10"
+	et "github.com/go-playground/validator/v10/translations/en"
+)
+
+func Validate(object interface{}) (errs []string){
+	validate, trans := getValidator()
+	err := validate.Struct(object)
+	return translateError(err, trans)
+}
+
+func translateError(err error, trans *ut.Translator) (errs []string) {
+	if err == nil {
+		return nil
+	}
+	validatorErrs := err.(validator.ValidationErrors)
+	for _, e := range validatorErrs {
+		translatedErr := fmt.Errorf(e.Translate(*trans)).Error()
+		errs = append(errs, translatedErr)
+	}
+	return errs
+}
+
+func getValidator() (*validator.Validate, *ut.Translator) {
+	validate := validator.New()
+	english := en.New()
+	trans, _ := ut.New(english, english).GetTranslator("en")
+	_ = et.RegisterDefaultTranslations(validate, trans)
+	return validate, &trans
+}