Add Loki support to Telegraf interface

[pcarinhas]

Important notices

• [* ] I have read the contributing guide lines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• [ *] I am convinced that my issue is new after having checked both open and closed issues at https://github.com/opnsense/core/issues?q=is%3Aissue

Is your feature request related to a problem? Please describe.

Getting metrics/logs into Loki is a pain. We can write our own configuration file for Telegraf, but that
is probematic and goes against the OpnSense way.

Describe the solution you like

Add Loki support to the Telegraf plugin, and ensure it has options to include the Loki bearer_token so that
it is secure.

Describe alternatives you considered

Writing a custom Telegraf configuration file and inserting that into the OpnSense directly. Its probably not a stable way to go. Other solution is to create a Fluent-bit package (I created a separate feature request for this).

Additional context
Loki is lightweight and powerful on its own. It provides a general and scalable way to monitor both logs and metrics. Its worthwhile to have Loki support inside of OpnSense.

[AdSchellevis]

moved to #4407, please open future plugin tickets in this repository

[pcarinhas]

Thank, I will.

Also, there are several ways to authenticate to Loki, many use Nginx and basic auth, but a bearer token can be used as well:

Bearer Token

[[outputs.loki]]
  endpoint = "https://your_loki_server:3100/loki/api/v1/push"
  headers = [
    {"Authorization": "Bearer your_token"}
  ]
  labels = ["job=pfsense"]

Basic Auth

[[outputs.loki]]
  endpoint = "https://your_loki_server:3100/loki/api/v1/push"
  username = "your_username"
  password = "your_password"
  labels = ["job=pfsense"]

[pcarinhas]

One more comment. It may be enough, in the short run, to provide a custom configuration textbox in the outputs section of the configuration, that writes the appropriate place.

[AdSchellevis]

One more comment. It may be enough, in the short run, to provide a custom configuration textbox in the outputs section of the configuration, that writes the appropriate place.

Although I'm not involved in development of this plugin, free text unvalidated input doesn't meet the bar (https://docs.opnsense.org/development/guidelines/basics.html#safeguard-user-input)

[mimugmail]

Its not that hard, do you want to try it on your own?

https://github.com/opnsense/plugins/pull/3607/files