New endpoint: Send MOTD as email

[i-oden]

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Description

In order to perform maintenance or redeploy the DDS safely and avoid users performing tasks close to it, we need to be a able to inform the users of when the DDS will be down. Sometimes a MOTD unrelated to maintenance may also be very important and sending it as an email will increase the probability of one of the users reading it.

This PR adds a new endpoint which creates a connection to the email server and sends one email to each users primary email.

• Add a summary of the changes and the related issue
• Add motivation and context regarding why the change is needed
• Fixes DDS-1349 (part of DDS-1326)

Type of change

• New feature (non-breaking)

Checklist:

General

• Changelog: New row added
• Code change
  • Self-review of code done
  • Comments added, particularly in hard-to-understand areas

Repository / Releases

• Blocking PRs have been merged
• Rebase / update of branch done

Checks

• Formatting: Black & Prettier checks pass
• CodeQL passes
• Tests
  • I have added tests for the new code
  • The tests pass
• Trivy / Snyk:
  • There are no new security alerts

[codecov]

Codecov Report

Merging #1283 (ef5e104) into dev (040f263) will increase coverage by 0.10%.
The diff coverage is 88.88%.

❗ Current head ef5e104 differs from pull request most recent head b6124f3. Consider uploading reports for the commit b6124f3 to get more accurate results

@@            Coverage Diff             @@
##              dev    #1283      +/-   ##
==========================================
+ Coverage   87.53%   87.63%   +0.10%     
==========================================
  Files          29       29              
  Lines        3875     3907      +32     
==========================================
+ Hits         3392     3424      +32     
  Misses        483      483              

Impacted Files	Coverage Δ
dds_web/utils.py	95.66% <58.33%> (-1.86%)	⬇️
dds_web/api/__init__.py	100.00% <100.00%> (ø)
dds_web/api/superadmin_only.py	100.00% <100.00%> (ø)
dds_web/api/user.py	89.23% <100.00%> (+0.81%)	⬆️

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