COPY handle no fields

[mbeynon]

✓ Checklist:

• This PR has been added to CHANGELOG.md (at the top of the list);
• Tests for the changes have been added (for bug fixes / features);
• Docs have been added / updated (for bug fixes / features).

See issue #146 for more information

[evgeniy-r]

Hello!

Thank you for your contribution!
Could you please fix the rustfmt/clippy warnings?
And also add unit tests and update CHANGELOG.md?

May I ask you to attach your database schema (without data) or at least the related part?

[codecov-commenter]

Codecov Report

Merging #147 (a44dafa) into main (8d531f3) will increase coverage by 0.04%.
The diff coverage is 95.83%.

@@            Coverage Diff             @@
##             main     #147      +/-   ##
==========================================
+ Coverage   85.94%   85.99%   +0.04%     
==========================================
  Files          52       52              
  Lines        3187     3205      +18     
==========================================
+ Hits         2739     2756      +17     
- Misses        448      449       +1     

Impacted Files	Coverage Δ
datanymizer_dumper/src/postgres/table.rs	95.31% <95.83%> (-0.06%)	⬇️

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[mbeynon]

Example schema.dump and config (test1.yaml) that shows the problem with schema_3.table_3_1 that has no fields

schema.dump.txt
test1.yaml.txt

[mbeynon]

The PR is now ready to merge