Add user object to the filter namespace

[wolneykien]

The current evaluation context of the filter function defined for an ApiUser doesn't provide any way to access the user object itself.

With the patch applied the problem of having an ApiUser per Host (see https://community.icinga.com/t/per-host-api-user-for-passive-check-submission/9053/3 , for instance) can be solved by first defining a template like this:

template ApiUser "usersync" {
  permissions = [{
    permission = "actions/process-check-result"
    filter = () => {
      return host.name == user.client_cn
    }
  }]
}

And then by creating an ApiUser that imports it, possibly using the REST API. I. e.:

curl ... -X PUT 'https://localhost:5665/v1/objects/apiusers/userforhost1' -d '{"attrs": {"client_cn": "host1"}, "templates": ["usersync"]}'

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[Al2Klimov]

Didn't test, but I could imagine that it also works like this:

• At the beginning of the template get the user: var user = this
• Capture that var in the filter closure: use(user)