[#125] node: Move viper creation to internal/common/config

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

cmd/internal/common/config/opts.go

@@ -0,0 +1,38 @@
+package config
+
+type Opts struct {
+	Path      string
+	ConfigDir string
+	EnvPrefix string
+}
+
+func DefaultOpts() *Opts {
+	return new(Opts)
+}
+
+// Option allows to set an optional parameter of the Config.
+type Option func(*Opts)
+
+// WithConfigFile returns an option to set the system path
+// to the configuration file.
+func WithConfigFile(path string) Option {
+	return func(o *Opts) {
+		o.Path = path
+	}
+}
+
+// WithConfigDir returns an option to set the system path
+// to the directory with configuration files.
+func WithConfigDir(path string) Option {
+	return func(o *Opts) {
+		o.ConfigDir = path
+	}
+}
+
+// WithEnvPrefix returns an option to defines
+// a prefix that ENVIRONMENT variables will use.
+func WithEnvPrefix(envPrefix string) Option {
+	return func(o *Opts) {
+		o.EnvPrefix = envPrefix
+	}
+}