🐛 Fix needextract

[chrisjsewell]

• remove content_id
• rename content_node -> node_copy
• move needextract specific code to needextract.py
• use warnings instead of raising

[codecov]

Codecov Report

Attention: Patch coverage is 82.14286% with 10 lines in your changes missing coverage. Please review.

Project coverage is 86.35%. Comparing base (ac2d3e6) to head (6800428).
Report is 1 commits behind head on master.

Files	Patch %	Lines
sphinx_needs/directives/needextract.py	86.95%	6 Missing ⚠️
sphinx_needs/data.py	50.00%	2 Missing ⚠️
sphinx_needs/layout.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1198      +/-   ##
==========================================
- Coverage   86.44%   86.35%   -0.10%     
==========================================
  Files          56       56              
  Lines        6501     6508       +7     
==========================================
  Hits         5620     5620              
- Misses        881      888       +7     

Flag	Coverage Δ
pytests	86.35% <82.14%> (-0.10%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.