Only one user can mark an alert as ignored

Thanks for this great module! The "Mark as ignored" / "Mark as OK" functionality looks really handy!

Problem

It looks like only one user can mark an alert as "Ignored". If two users mark the same alert as "Ignored" then it will still show up as active for one of them.

Steps to reproduce

• Create content with an accessibility alert:
  1. Enable editoria11y module
  2. Go to /node/add/page
  3. Create a page with an accessibility alert (e.g. skip a heading level)
• Create 2 users (say, UserA and UserB):
  1. Go to /admin/people/create
  2. Create the 2 users
  3. Grant the permissions below to these 2 users:
     • View Editoria11y checker
     • Mark as hidden in Editoria11y
     • Manage Editoria11y results
• Make UserA ignore the alert:
  1. Sign in as UserA
  2. View the page - Editoria11y will report the accessibility alert
  3. Click "Mark as Ignored" - this will clear the alert as expected
  4. Go to /admin/reports/editoria11y/dismissals - the alert will be listed as hidden by UserA as expected
• Make UserB ignore the alert:
  1. Sign in as UserB
  2. View the page - Editoria11y will report the accessibility alert
  3. Click "Mark as Ignored" - this will clear the alert as expected
  4. Go to /admin/reports/editoria11y/dismissals
     • Expected result: the alert will be listed as hidden by both UserA and UserB
     • Actual result: the alert is listed as hidden only by UserA
• Check whether the alert is still ignored by UserA:
  1. Sign in as UserA
  2. View the page
     • Expected result: the alert is still ignored
     • Actual result: the alert is now active (yellow)

In a nutshell:

Proposed resolution

I am guessing the database model should allow for multiple users to ignore the same alert ID.