feat: Add GraphQL notification settings for MS Teams and Mattermost

[Dschoordsch]

Description

Partially Fixes #10647
Adding the GraphQL types for notification settings for Mattermost and MS Teams.
The UI and honouring the settings in the notification manager will be done separately.

Demo

[If possible, please include a screenshot or gif/video, it'll make it easier for reviewers to understand the scope of the changes and how the change is supposed to work. If you're introducing something new or changing the existing patterns, please share a Loom and explain what decisions you've made and under what circumstances]

Testing scenarios

mutation NotificationSettings {
  setNotificationSetting(
    authId: "TeamMemberIntegrationAuth:1"
    event: meetingEnd
    isEnabled: false
  ) {
    __typename
    ...on ErrorPayload {
      error {
        message 
      }
    }
    ...on SetNotificationSettingSuccess {
      authId
      auth {
        id
        ...on TeamMemberIntegrationAuthWebhook {
          events
        }
      }
    }
  }  
}

Final checklist

• I checked the code review guidelines
• I have added Metrics Representative as reviewer(s) if my PR invovles metrics/data/analytics related changes
• I have performed a self-review of my code, the same way I'd do it for any other team member
• I have tested all cases I listed in the testing scenarios and I haven't found any issues or regressions
• Whenever I took a non-obvious choice I added a comment explaining why I did it this way
• I added the label Skip Maintainer Review Indicating the PR only requires reviewer review and can be merged right after it's approved if the PR introduces only minor changes, does not contain any architectural changes or does not introduce any new patterns and I think one review is sufficient'
• PR title is human readable and could be used in changelog