gitlab-org--gitlab-foss/app/assets/javascripts/sidebar/queries/update_issue_subscription.mutation.graphql

mutation projectIssueSetSubscription($fullPath: ID!, $iid: String!, $subscribedState: Boolean!) {
  updateIssuableSubscription: issueSetSubscription(
    input: { projectPath: $fullPath, iid: $iid, subscribedState: $subscribedState }
  ) {
    issuable: issue {
      id
      subscribed
    }
    errors
  }
}