Port Python test to Elixir: `07_text_custom_field_list_test`

[AlbaHerrerias]

Overview

This work is done according to "Milestone 3. Convert Python test suite to eunit or exunit" as stated in the Scope of Work with Sovereign Tech Agency Resilience Program.

This PR includes:

• Port 07-text-custom-field-list-test.py test to Elixir
• Remove corresponding python test

Please note that some tests are not ported. For further explanation, search for the TODO keyword in the test file.

Testing recommendations

Run:

make elixir-search

or

make elixir-search test/elixir/test/mango/07_text_custom_field_list_test.exs

Related Issues or Pull Requests

https://github.com/apache/couchdb/pull/5753

Checklist

• [ ] Code is written and works correctly
• [ ] Changes are covered by tests
• [ ] Any new configurable parameters are documented in rel/overlay/etc/default.ini
• [ ] Documentation changes were made in the src/docs folder
• [ ] Documentation changes were backported (separated PR) to affected branches