Adapt MOTD endpoint for displaying motd in cli

[valyo]

Adapt MOTD endpoint for displaying motd in cli

Works with ScilifelabDataCentre/dds_cli#498

Please include the following in this section

• Summary of the changes and the related issue
• Relevant motivation and context
• Any dependencies that are required for this change

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

Please delete options that are not relevant.

• Any dependent changes have been merged and published in downstream modules
• Rebase/merge the branch which this PR is made to
• Changes to the database schema: A new migration is included in the PR

Formatting and documentation

• I have added a row in the changelog
• The code follows the style guidelines of this project: Black / Prettier formatting
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

Tests

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov]

Codecov Report

Merging #1198 (feb9563) into dev (12a0f4a) will increase coverage by 0.29%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev    #1198      +/-   ##
==========================================
+ Coverage   85.89%   86.18%   +0.29%     
==========================================
  Files          30       30              
  Lines        3735     3743       +8     
==========================================
+ Hits         3208     3226      +18     
+ Misses        527      517      -10     

Impacted Files	Coverage Δ
dds_web/__init__.py	60.00% <100.00%> (ø)
dds_web/api/__init__.py	100.00% <100.00%> (ø)
dds_web/api/superadmin_only.py	100.00% <100.00%> (+30.30%)	⬆️
dds_web/utils.py	97.27% <100.00%> (+0.03%)	⬆️

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[i-oden]

Looks good, will test after lunch. Could you add some tests as well?