[FEATURE] Integration with other notification services like Apprise & Shoutrrr

[just5ky]

Is your feature request related to a problem?

• Lack of pre-defined notification endpoints.

What solution would you like?

• Integration with open source software such as Apprise or Shoutrrr

What alternatives have you considered?

• Using custom webhooks option is not easy.

Do you have any additional context?

• Apps like Apprise has predefined configurations for a lot of popular notification endpoints
• Other people are also requesting for more endpoints opensearch-project/alerting#464

Edit: Some more references

• https://github.com/caronc/apprise/wiki
• https://github.com/caronc/apprise-api

[praveensameneni]

Thank you for the enhancement request. We are adding this to our backlog.

[brijos]

Tagging https://github.com/opensearch-project/notifications/issues/674. We need a focused effort to improve predefined notification endpoints.