Disentangle the api abilities from the web abilities

This will allow us to rename api actions without causing permissions headaches. The choice of
abilities files is made by inheriting from either api_controller or application_controller.

Also rename capabilities to api_capabilites, for consistency.

test/abilities/api_abilities_test.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class ApiAbilityTest < ActiveSupport::TestCase
+end
+
+class GuestApiAbilityTest < ApiAbilityTest
+  test "note permissions for a guest" do
+    ability = ApiAbility.new nil
+
+    [:index, :create, :comment, :feed, :show, :search].each do |action|
+      assert ability.can?(action, Note), "should be able to #{action} Notes"
+    end
+
+    [:close, :reopen, :destroy].each do |action|
+      assert ability.cannot?(action, Note), "should not be able to #{action} Notes"
+    end
+  end
+end
+
+class UserApiAbilityTest < ApiAbilityTest
+  test "Note permissions" do
+    ability = ApiAbility.new create(:user)
+
+    [:index, :create, :comment, :feed, :show, :search, :close, :reopen].each do |action|
+      assert ability.can?(action, Note), "should be able to #{action} Notes"
+    end
+
+    [:destroy].each do |action|
+      assert ability.cannot?(action, Note), "should not be able to #{action} Notes"
+    end
+  end
+end
+
+class ModeratorApiAbilityTest < ApiAbilityTest
+  test "Note permissions" do
+    ability = ApiAbility.new create(:moderator_user)
+
+    [:index, :create, :comment, :feed, :show, :search, :close, :reopen, :destroy].each do |action|
+      assert ability.can?(action, Note), "should be able to #{action} Notes"
+    end
+  end
+end