Refactor: Convert TODO Comments Into Issues

[haricnugraha]

Monika Pull Request (PR)

What feature/issue does this PR add

• Convert a TODO comment into an issue #1260.
• Make the hardcoded notification sender changeable through a parameter.
• Separate sending error notification for the TLS checker function due to poor abstraction.
• Remove irrelevant TODO comments.

It will resolve #1010.

How to test

Run the following configuration. You should receive a TLS error notification (Please set your own notification):

probes:
  - id: example
    requests:
      - url: 'https://example.com'
certificate:
  domains:
    - example.com
    - expired.badssl.com
  reminder: 30

Before

After (unchanged)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 42.30769% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 62.60%. Comparing base (3d2380c) to head (e7d8dfb).

Files	Patch %	Lines
src/jobs/tls-check.ts	37.50%	10 Missing :warning:
packages/notification/utils/default-sender.ts	60.00%	2 Missing :warning:
packages/notification/channel/mailgun.ts	50.00%	1 Missing :warning:
packages/notification/channel/smtp.ts	50.00%	1 Missing :warning:
src/utils/open-website.ts	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1262 +/- ## ========================================== + Coverage 62.37% 62.60% +0.23% ========================================== Files 111 112 +1 Lines 3378 3391 +13 Branches 590 589 -1 ========================================== + Hits 2107 2123 +16 + Misses 1080 1072 -8 - Partials 191 196 +5 ```

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