Pipelines email service API returns `"true"` instead of `true`

Summary

The GET pipeline-emails API returns the string "true" instead of true for the notify_only_broken_pipelines field.

Steps to reproduce

Create a pipelines emails integration for a project in the UI, and run:

curl API_URL/projects/PROJECT/services/pipelines-email?private_token=TOKEN

Example Project

https://gitlab.com/jeremad/test

curl https://gitlab.com/api/v4/projects/19032531/services/pipelines-email?private_token=...

What is the current bug behavior?

The API returns:

{...,
  "properties": {
    "recipients": "...",
    "notify_only_broken_pipelines": "true",
    "branches_to_be_notified": "default"
  }
}

What is the expected correct behavior?

The API should return:

{...,
  "properties": {
    "recipients": "...",
    "notify_only_broken_pipelines": true,
    "branches_to_be_notified": "default"
  }
}

Possible resolution

After a brief look at the code, it seems all services integration are affected