Update structure to domain driven architecture.

tui/ui.go

@@ -0,0 +1,23 @@
+package tui
+
+import (
+	// "nfeeder/tui/pages"
+)
+
+type sessionState int
+
+const (
+	LoginView sessionState = iota
+	FeedView
+	HelpView
+)
+
+type MainModel struct {
+	state  sessionState
+	width  int
+	height int
+
+	// Sub-models
+	loginPage pages.LoginModel
+	feedPage  pages.FeedModel
+}