e2e-Test for partial find behavior

[mmaelicke]

This tests covers a partial entry within a Composite entry. With api.find_entry() it is not found, but with `api.find_entry(include_partial=True) it is found.

Closes #151

For the CLI:

• [x] add the --include-partial flag to find CLI

[codecov[bot]]

Codecov Report

Merging #153 (c9f365a) into master (bf48511) will increase coverage by 0.03%. The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #153      +/-   ##
==========================================
+ Coverage   63.38%   63.42%   +0.03%     
==========================================
  Files          66       66              
  Lines        3062     3065       +3     
==========================================
+ Hits         1941     1944       +3     
  Misses       1121     1121              

Flag	Coverage Δ
e2e	63.42% <66.66%> (+0.03%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
metacatalog/cmd/find.py	41.17% <50.00%> (+0.26%)	:arrow_up:
metacatalog/command_line.py	89.87% <100.00%> (+0.12%)	:arrow_up:
metacatalog/api/find.py	58.21% <0.00%> (+0.34%)	:arrow_up:

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[mmaelicke]

@AlexDo1 this PR looks good to me. You can check the code changes in the find_entry API and approve if there are no comments.