feat: add nats service

[tombojer]

This pull request introduces a new notification service for NATS, adding support for sending messages via NATS.

Parameters

This notification service is capable of sending simple messages via Nats.

• Url - Nats server URL, e.g. nats://nats:4222
• Headers - optional, additional headers to be sent with the message
• User - optional, Nats user for authentication used in combination with password
• Password - optional, Nats password for authentication used in combination with user
• Nkey - optional, Nats key for authentication

Example

Resource Annotation:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  annotations:
    notifications.argoproj.io/subscribe.on-deployment-ready.nats: "mytopic"

• ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-notifications-cm
data:
  service.nats: |
    url: "nats://nats:4222"
    headers:
      my-header: "my-value"

template.deployment-ready: |
    message: |
      Deployment {{.obj.metadata.name}} is ready!

  trigger.on-deployment-ready: |
    - when: any(obj.status.conditions, {.type == 'Available' && .status == 'True'})
      send: [deployment-ready]
    - oncePer: obj.metadata.annotations["generation"]

[codecov]

Codecov Report

❌ Patch coverage is 63.88889% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.02%. Comparing base (da04400) to head (776125e).
⚠️ Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/services/nats.go	74.19%	4 Missing and 4 partials ⚠️
pkg/services/services.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #380      +/-   ##
==========================================
+ Coverage   55.41%   60.02%   +4.60%     
==========================================
  Files          46       48       +2     
  Lines        4125     3655     -470     
==========================================
- Hits         2286     2194      -92     
+ Misses       1511     1111     -400     
- Partials      328      350      +22     

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[pasha-codefresh]

@tombojer could you please fix linter issues?

[tombojer]

@pasha-codefresh The tests are now passing.

Ping me if I need to do something else.