login: refactor login form to use simple form.

Also change form to pass params as e.g. `session[name]` instead of just
`name`.

app/controllers/sessions_controller.rb

@@ -7,11 +7,12 @@ class SessionsController < ApplicationController
   end
 
   def create
-    session_creator = SessionCreator.new(session, params[:name], params[:password], request.remote_ip)
+    session_params = params[:session].presence || params
+    session_creator = SessionCreator.new(session, session_params[:name], session_params[:password], request.remote_ip)
 
     if session_creator.authenticate
-      url = params[:url] if params[:url] && params[:url].start_with?("/")
-      url = posts_path if url.nil?
+      url = session_params[:url]
+      url = posts_path if !url&.start_with?("/")
       respond_with(session_creator.user, location: url, methods: [:api_token])
     else
       flash.now[:notice] = "Password was incorrect"

app/views/sessions/new.html.erb

@@ -2,28 +2,17 @@
   <div id="a-new">
     <section>
       <h1>Sign in</h1>
-      <%= form_tag(session_path, :class => "simple_form") do %>
-        <%= hidden_field_tag "url", params[:url] %>
 
-        <div class="input">
-          <label for="name">Name</label>
-          <%= text_field_tag :name %>
-        </div>
-
-        <div class="input">
-          <label for="password">Password</label>
-          <%= password_field_tag :password %>
-        </div>
-
-        <p class="fineprint">
-          New to <%= Danbooru.config.app_name %>? <%= link_to "Create a new account", new_user_path %>.
-        </p>
-
-        <div class="input">
-          <%= submit_tag "Submit", :data => { :disable_with => "Signing in..." } %>
-        </div>
+      <%= simple_form_for(:session, url: session_path) do |f| %>
+        <%= f.input :url, as: :hidden, input_html: { value: params[:url] } %>
+        <%= f.input :name %>
+        <%= f.input :password, input_html: { autocomplete: "password" } %>
+        <%= f.submit "Login" %>
       <% end %>
-    </section>
+
+      <p class="fineprint">
+        New to <%= Danbooru.config.app_name %>? <%= link_to "Create a new account", new_user_path %>.
+      </p>
   </div>
 </div>