Improve implementation around config (#1122)

* refactor config

* fix saas config

* feat(config): scanmodule for each server in config.toml

* feat(config): enable to specify containersOnly in config.toml

* add new keys of config.toml to discover.go

* fix summary output, logging

config/httpconf.go

@@ -0,0 +1,38 @@
+package config
+
+import (
+	"os"
+
+	"github.com/asaskevich/govalidator"
+)
+
+// HTTPConf is HTTP config
+type HTTPConf struct {
+	URL string `valid:"url" json:"-"`
+}
+
+// Validate validates configuration
+func (c *HTTPConf) Validate() (errs []error) {
+	if !Conf.ToHTTP {
+		return nil
+	}
+
+	if _, err := govalidator.ValidateStruct(c); err != nil {
+		errs = append(errs, err)
+	}
+	return errs
+}
+
+const httpKey = "VULS_HTTP_URL"
+
+// Init set options with the following priority.
+// 1. Environment variable
+// 2. config.toml
+func (c *HTTPConf) Init(toml HTTPConf) {
+	if os.Getenv(httpKey) != "" {
+		c.URL = os.Getenv(httpKey)
+	}
+	if toml.URL != "" {
+		c.URL = toml.URL
+	}
+}