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/saasconf.go

@@ -0,0 +1,34 @@
+package config
+
+import (
+	"github.com/asaskevich/govalidator"
+	"golang.org/x/xerrors"
+)
+
+// SaasConf is FutureVuls config
+type SaasConf struct {
+	GroupID int64  `json:"-"`
+	Token   string `json:"-"`
+	URL     string `json:"-"`
+}
+
+// Validate validates configuration
+func (c *SaasConf) Validate() (errs []error) {
+	if c.GroupID == 0 {
+		errs = append(errs, xerrors.New("GroupID must not be empty"))
+	}
+
+	if len(c.Token) == 0 {
+		errs = append(errs, xerrors.New("Token must not be empty"))
+	}
+
+	if len(c.URL) == 0 {
+		errs = append(errs, xerrors.New("URL must not be empty"))
+	}
+
+	_, err := govalidator.ValidateStruct(c)
+	if err != nil {
+		errs = append(errs, err)
+	}
+	return
+}