Implement sessions/create in JSON API

spec/integration/api/v0/api_sign_in_spec.rb

@@ -0,0 +1,29 @@
+require 'spec_helper'
+
+feature 'API sign in' do
+  let(:user)  { Factory.create(:user) }
+
+  def do_create
+    post api_v0_sessions_path, :format => :json, :session => {
+      :email    => user.email,
+      :password => user.password
+    }
+  end
+
+  scenario 'signs the user in with valid credentials' do
+    do_create
+
+    response.should be_success
+    (JSON response.body).should include 'id'
+  end
+
+  [:email, :password].each do |attr|
+    scenario "rejects authentication with invalid credentials (#{attr})" do
+      user.stub(attr => user.send(attr) + '_INVALID')
+      do_create
+
+      response.should be_not_found
+      response.body.should be_empty
+    end
+  end
+end