Surface real error when saving a security attribute fails

What does this MR do?

When creating a security attribute fails — for example, when adding one would exceed the per-category attribute limit — the UI showed a generic banner ("An error has occurred while saving the security attribute.") even though the GraphQL response contained the specific, actionable message ("Category cannot have more than N attributes.").

The backend is correct: the limit is enforced in Mutations::Security::Attributes::Create#validate_category_attribute_limit, which raises a top-level GraphQL error. The bug was purely frontend — saveAttribute() in configure_attributes.vue hard-coded the generic message and ignored error.message, unlike the sibling saveCategory() which handles it correctly.

Changes

• configure_attributes.vue:
  • Catch block now falls back to error?.message before the generic string, so the real error is shown.
  • Both create and update .then blocks now check the mutation payload errors array and throw the first error (mirroring saveCategory), covering service-level validation errors returned in the payload.
• Tests: converted the attribute-failure test into an it.each covering the payload-errors path, a top-level rejection carrying a message, and the generic fallback. Also fixed the test to let the group query resolve before saving (previously it threw on selectedCategory.id and never exercised the mutation).

Testing

jest ee/spec/frontend/security_configuration/components/security_attributes/configure_attributes_spec.js — 19 examples, 0 failures. ESLint and Prettier clean.

Screenshots or screen recordings

How to setup and validate locally

1. In the rails console, create a category and add the limit of 100 attributes to it

namespace = Namespace.find 33 # flightjs on my GDK

categories = 1
attributes =  100
categories.times do |c|

category = Security::Category.create!(
		name: "cat-#{c + 10}",
		editable_state:    :editable,
		namespace: namespace
		)

#color per category
color = SecureRandom.hex(3)

	attributes.times do |a|
	Security::Attribute.create!(
			name:              "#{a + 1}-attr, cat-#{c + 1}  ",
			description:       "Generated attribute #{a + 1}",
			color:             "##{color}",
			editable_state:    :editable,
			security_category: category,
			namespace:         namespace
			)
	end
end

2. Navigate to FlightJS group -> Security configuration menu item -> Security Attributes tab
3. Attempt to create the 101st attribute
4. Observe the improved error message

References

No related issue. I discovered the bug while working on something else and opened an MR for it.

	Before	After
Attempting to add an attribute goes over the limit