FEATURE: Show error if invite to topic is invalid (#15959)

This can happen if the topic to which a user is invited is in a private
category and the user was not invited to one of the groups that can see
that specific category.

This used to be a warning and this commit makes it an error.

spec/models/invite_spec.rb

@@ -429,27 +429,4 @@ describe Invite do
       expect(invite.invalidated_at).to be_nil
     end
   end
-
-  describe '#warnings' do
-    fab!(:admin) { Fabricate(:admin) }
-    fab!(:invite) { Fabricate(:invite) }
-    fab!(:group) { Fabricate(:group) }
-    fab!(:secured_category) do
-      secured_category = Fabricate(:category)
-      secured_category.permissions = { group.name => :full }
-      secured_category.save!
-      secured_category
-    end
-
-    it 'does not return any warnings for simple invites' do
-      expect(invite.warnings(admin.guardian)).to be_blank
-    end
-
-    it 'returns a warning if topic is private' do
-      topic = Fabricate(:topic, category: secured_category)
-      TopicInvite.create!(topic: topic, invite: invite)
-
-      expect(invite.warnings(admin.guardian)).to contain_exactly(I18n.t("invite.requires_groups", groups: group.name))
-    end
-  end
 end

spec/requests/invites_controller_spec.rb

@@ -203,6 +203,35 @@ describe InvitesController do
         post '/invites.json', params: { email: 'test@example.com', topic_id: -9999 }
         expect(response.status).to eq(400)
       end
+
+      context 'topic is private' do
+        fab!(:group) { Fabricate(:group) }
+
+        fab!(:secured_category) do |category|
+          category = Fabricate(:category)
+          category.permissions = { group.name => :full }
+          category.save!
+          category
+        end
+
+        fab!(:topic) { Fabricate(:topic, category: secured_category) }
+
+        it 'does not work and returns a list of required groups' do
+          sign_in(admin)
+
+          post '/invites.json', params: { email: 'test@example.com', topic_id: topic.id }
+          expect(response.status).to eq(422)
+          expect(response.parsed_body["errors"]).to contain_exactly(I18n.t("invite.requires_groups", groups: group.name))
+        end
+
+        it 'does not work if user cannot edit groups' do
+          group.add(user)
+          sign_in(user)
+
+          post '/invites.json', params: { email: 'test@example.com', topic_id: topic.id }
+          expect(response.status).to eq(403)
+        end
+      end
     end
 
     context 'invite to group' do