feat(user-sessions): implement user login, logout, and session management

knockoutwhistweb/app/views/login.scala.html

@@ -0,0 +1,18 @@
+@()
+
+@main("Login") {
+    <div class="container">
+        <h2>Login</h2>
+        <form action="@routes.UserController.login_Post()" method="post">
+            <div class="form-group">
+                <label for="username">Username:</label>
+                <input type="text" class="form-control" id="username" name="username" required>
+            </div>
+            <div class="form-group">
+                <label for="password">Password:</label>
+                <input type="password" class="form-control" id="password" name="password" required>
+            </div>
+            <button type="submit" class="btn btn-primary">Login</button>
+        </form>
+    </div>
+}