Fix Ember warnings about embedded data not being present on APIs.

src/api-umbrella/web-app/app/models/api.rb

@@ -280,4 +280,17 @@ def roles
     roles.uniq!
     roles
   end
+
+  def serializable_hash(options = nil)
+    hash = super(options)
+    # Ensure all embedded relationships are at least null in the JSON output
+    # (rather than not being present), or else Ember-Data's serialization
+    # throws warnings.
+    hash["rewrites"] ||= nil
+    hash["servers"] ||= nil
+    hash["settings"] ||= nil
+    hash["sub_settings"] ||= nil
+    hash["url_matches"] ||= nil
+    hash
+  end
 end

src/api-umbrella/web-app/app/models/api/settings.rb

@@ -134,6 +134,18 @@ def set_transition_starts_on_publish
     end
   end
 
+  def serializable_hash(options = nil)
+    hash = super(options)
+    # Ensure all embedded relationships are at least null in the JSON output
+    # (rather than not being present), or else Ember-Data's serialization
+    # throws warnings.
+    hash["default_response_headers"] ||= nil
+    hash["headers"] ||= nil
+    hash["override_response_headers"] ||= nil
+    hash["rate_limits"] ||= nil
+    hash
+  end
+
   private
 
   def read_headers_string(field)

src/api-umbrella/web-app/app/models/api/sub_settings.rb

@@ -16,4 +16,13 @@ class Api::SubSettings
 
   # Nested attributes
   accepts_nested_attributes_for :settings
+
+  def serializable_hash(options = nil)
+    hash = super(options)
+    # Ensure all embedded relationships are at least null in the JSON output
+    # (rather than not being present), or else Ember-Data's serialization
+    # throws warnings.
+    hash["settings"] ||= nil
+    hash
+  end
 end

src/api-umbrella/web-app/app/models/api_user.rb

@@ -130,6 +130,15 @@ def api_key_hides_at
     @api_key_hides_at ||= self.created_at + 2.weeks
   end
 
+  def serializable_hash(options = nil)
+    hash = super(options)
+    # Ensure all embedded relationships are at least null in the JSON output
+    # (rather than not being present), or else Ember-Data's serialization
+    # throws warnings.
+    hash["settings"] ||= nil
+    hash
+  end
+
   private
 
   def normalize_terms_and_conditions