[#1161] Added 'description' to Plan model, 'goal' and 'description' to Plan forms & views

[Bartvaderkin]

Note this is based on PR #494 because it touches the same views, migrations etc.

For review I set the merge target to that same branch; iirc Github will update it once that lands.

[codecov-commenter]

Codecov Report

Merging #497 (0953e69) into feature/1162-remove-goal-from-actions (ff4e8aa) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@                            Coverage Diff                            @@
##           feature/1162-remove-goal-from-actions     #497      +/-   ##
=========================================================================
- Coverage                                  96.52%   96.51%   -0.01%     
=========================================================================
  Files                                        516      517       +1     
  Lines                                      18719    18587     -132     
=========================================================================
- Hits                                       18069    17940     -129     
+ Misses                                       650      647       -3     

Impacted Files	Coverage Δ
src/open_inwoner/plans/forms.py	100.00% <100.00%> (ø)
...nwoner/plans/migrations/0013_auto_20230223_1115.py	100.00% <100.00%> (ø)
src/open_inwoner/plans/models.py	98.52% <100.00%> (+0.04%)	⬆️
src/open_inwoner/plans/tests/factories.py	100.00% <100.00%> (ø)
src/open_inwoner/plans/tests/test_logging.py	100.00% <100.00%> (ø)
src/open_inwoner/plans/tests/test_views.py	100.00% <100.00%> (ø)
...c/open_inwoner/utils/tests/test_timeline_logger.py	100.00% <100.00%> (ø)
.../open_inwoner/components/templatetags/form_tags.py	94.30% <0.00%> (-0.82%)	⬇️
src/open_inwoner/plans/views.py	97.83% <0.00%> (-0.30%)	⬇️
... and 6 more

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