api keys: add IP whitelist and API permission system.

Add the ability to restrict API keys so that they can only be used with
certain IP addresses or certain API endpoints.

Restricting your key is useful to limit damage in case it gets leaked or
stolen. For example, if your key is on a remote server and it gets
hacked, or if you accidentally check-in your key to Github.

Restricting your key's API permissions is useful if a third-party app or
script wants your key, but you don't want to give full access to your
account.

If you're an app or userscript developer, and your app needs an API key
from the user, you should only request a key with the minimum
permissions needed by your app.

If you have a privileged account, and you have scripts running under
your account, you are highly encouraged to restrict your key to limit
damage in case your key gets leaked or stolen.

test/functional/api_keys_controller_test.rb

@@ -4,13 +4,10 @@ class ApiKeysControllerTest < ActionDispatch::IntegrationTest
   context "An api keys controller" do
     setup do
       @user = create(:user)
+      @api_key = create(:api_key, user: @user)
     end
 
     context "#index action" do
-      setup do
-        @api_key = create(:api_key, user: @user)
-      end
-
       should "let a user see their own API keys" do
         get_auth user_api_keys_path(@user.id), @user
 
@@ -40,20 +37,54 @@ class ApiKeysControllerTest < ActionDispatch::IntegrationTest
       end
     end
 
+    context "#new action" do
+      should "render for a Member user" do
+        get_auth new_user_api_key_path(@user.id), @user
+        assert_response :success
+      end
+
+      should "fail for an Anonymous user" do
+        get new_user_api_key_path(@user.id)
+        assert_response 403
+      end
+    end
+
     context "#create action" do
       should "create a new API key" do
-        post_auth user_api_keys_path(@user.id), @user
+        post_auth user_api_keys_path(@user.id), @user, params: { api_key: { name: "blah" }}
 
         assert_redirected_to user_api_keys_path(@user.id)
-        assert_equal(true, @user.api_keys.last.present?)
+        assert_equal("blah", @user.api_keys.last.name)
+      end
+    end
+
+    context "#edit action" do
+      should "render for the API key owner" do
+        get_auth edit_api_key_path(@api_key.id), @user
+        assert_response :success
+      end
+
+      should "fail for someone else" do
+        get_auth edit_api_key_path(@api_key.id), create(:user)
+        assert_response 403
+      end
+    end
+
+    context "#update action" do
+      should "render for the API key owner" do
+        put_auth api_key_path(@api_key.id), @user, params: { api_key: { name: "blah" }}
+
+        assert_redirected_to user_api_keys_path(@user.id)
+        assert_equal("blah", @api_key.reload.name)
+      end
+
+      should "fail for someone else" do
+        put_auth api_key_path(@api_key.id), create(:user)
+        assert_response 403
       end
     end
 
     context "#destroy" do
-      setup do
-        @api_key = create(:api_key, user: @user)
-      end
-
       should "delete the user's API key" do
         delete_auth api_key_path(@api_key.id), @user