Feature/list datasets

[pahatz]

Related issue(s) and PR(s)
This PR closes #388 .

Description
This PR extends the functionality of list to be able for the user to list the files that belong to a dataset as well as listing all the user's datasets.

How to test
Set-up the testing environment by running:

bash .github/integration/setup/setup.sh

After all services come up, test listing the user's datasets by running:

./sda-cli list -config testing/s3cmd-download.conf --datasets  -url http://localhost:8080

Test listing the files from a dataset by running:

./sda-cli list -config testing/s3cmd-download.conf -dataset https://doi.example/ty009.sfrrss/600.45asasga -url http://localhost:8080

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 20.37037% with 43 lines in your changes missing coverage. Please review.

Project coverage is 41.60%. Comparing base (461565a) to head (848d8a7).

Files	Patch %	Lines
list/list.go	0.00%	28 Missing and 3 partials ⚠️
sda_download/sda_download.go	50.00%	8 Missing and 3 partials ⚠️
helpers/helpers.go	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #415      +/-   ##
==========================================
- Coverage   42.23%   41.60%   -0.64%     
==========================================
  Files          13       13              
  Lines        1977     2024      +47     
==========================================
+ Hits          835      842       +7     
- Misses       1028     1063      +35     
- Partials      114      119       +5     

Flag	Coverage Δ
unittests	41.60% <20.37%> (-0.64%)	⬇️

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[kostas-kou]

Looks good and works nice