Handle passing an invalid related resource in include params

app/controllers/api/v1/base_controller.rb

@@ -11,6 +11,17 @@ class BaseController < ActionController::API
         render json: { "errors": [ { "title":  "Too many results" } ] }, status: :bad_request
       end
 
+      rescue_from JSONAPI::Serializer::UnsupportedIncludeError do |exception|
+        render json: {
+          "errors": [
+            {
+              "title":  "`#{exception.include_item}` is not in the list of supported relationships",
+              source: { pointer: "/include" }
+            }
+          ]
+        }, status: :bad_request
+      end
+
       private
 
       def current_account

spec/requests/open_ews_api/v1/jsonapi_spec.rb

@@ -0,0 +1,30 @@
+
+require "rails_helper"
+
+RSpec.resource "JSONAPI", document: false  do
+  get "/v1/beneficiaries/:id" do
+    it "supports include related resources" do
+      beneficiary = create(:beneficiary)
+      create(:beneficiary_address, beneficiary:)
+
+      set_authorization_header_for(beneficiary.account)
+      do_request(id: beneficiary.id, include: "addresses")
+
+      expect(response_status).to eq(200)
+      expect(response_body).to match_jsonapi_resource_schema("beneficiary")
+      expect(json_response.dig("included", 0).to_json).to match_api_response_schema("address")
+    end
+
+    it "handles passing an invalid related resource" do
+      beneficiary = create(:beneficiary)
+      create(:beneficiary_address, beneficiary:)
+
+      set_authorization_header_for(beneficiary.account)
+      do_request(id: beneficiary.id, include: "foobar")
+
+      expect(response_status).to eq(400)
+      expect(response_body).to match_api_response_schema("jsonapi_error")
+      expect(json_response.dig("errors", 0, "source", "pointer")).to eq("/include")
+    end
+  end
+end