Async email

[jyotigautam]

Why?

To send the email asynchronously to prevent breaking the order checkout flow.

This change addresses the need by:

Adding a worker under the supervisor to send order confirmation mails in the background.

delivers #163724078

Checklist

• [ ] I have read CONTRIBUTING.md.
• [ ] My code follows the style guidelines of this project.
• [ ] I have commented my code, particularly in hard-to-understand areas.
• [ ] My code does not generate any (new) credo and compile-time warnings.
• [ ] I have updated the documentation wherever necessary.
• [ ] I have added tests to cover my changes.

[codecov[bot]]

Codecov Report

Merging #468 into develop will decrease coverage by 0.07%. The diff coverage is 55.55%.

@@             Coverage Diff             @@
##           develop     #468      +/-   ##
===========================================
- Coverage     79.1%   79.03%   -0.08%     
===========================================
  Files          175      176       +1     
  Lines         2202     2208       +6     
===========================================
+ Hits          1742     1745       +3     
- Misses         460      463       +3

Impacted Files	Coverage Δ
apps/snitch_core/lib/core/application.ex	100% <ø> (ø)	:arrow_up:
...s/snitch_core/lib/core/domain/order/transitions.ex	42.39% <0%> (ø)	:arrow_up:
apps/snitch_core/lib/core/data/model/images.ex	95.65% <100%> (+0.19%)	:arrow_up:
...s/snitch_core/lib/core/tools/mailer/mail_worker.ex	25% <25%> (ø)

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