Link to dev instance added to allow testing

[i-oden]

Description

To allow us (and possibly users) to test the DDS without having access to the production version, e.g. before signing up or in the case of a new feature, I added the dev instance link and a check for "test-instance".

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

Fixes X

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• Any dependent changes have been merged and published in downstream modules
• Rebase/merge the branch which this PR is made to

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 #506 (7eeeafd) into dev (baebd50) will increase coverage by 0.02%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##              dev     #506      +/-   ##
==========================================
+ Coverage   41.41%   41.44%   +0.02%     
==========================================
  Files          29       29              
  Lines        2528     2531       +3     
==========================================
+ Hits         1047     1049       +2     
- Misses       1481     1482       +1     

Impacted Files	Coverage Δ
dds_cli/__init__.py	90.78% <66.66%> (-1.00%)	⬇️
dds_cli/motd_manager.py	75.00% <0.00%> (-3.58%)	⬇️
dds_cli/__main__.py	41.41% <0.00%> (+0.18%)	⬆️

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