Allow registered diagrams to be overridden.

[sidharthv96]

📑 Summary

Instead of throwing an error when an existing diagram is found with same ID, we log a warning and replace it with new one.

This is basically to allow the external flowchart-elk to override the internal fallback to dagre.

Closes #5051 (different approach for same feature)

📏 Design Decisions

This is simpler than the other implementation with priority based overriding.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
• 🔖 targeted develop branch

[codecov]

Codecov Report

Merging #5050 (38b3a20) into sidv/splitELK (0fec0ef) will increase coverage by 0.00%.
The diff coverage is 0.00%.

Additional details and impacted files

@@              Coverage Diff               @@
##           sidv/splitELK    #5050   +/-   ##
==============================================
  Coverage          44.36%   44.37%           
==============================================
  Files                 25       25           
  Lines               5218     5217    -1     
  Branches              25       25           
==============================================
  Hits                2315     2315           
+ Misses              2902     2901    -1     
  Partials               1        1           

Flag	Coverage Δ
unit	44.37% <0.00%> (+<0.01%)	⬆️

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

Files	Coverage Δ
packages/mermaid/src/diagram-api/diagramAPI.ts	58.82% <0.00%> (ø)
packages/mermaid/src/diagram-api/detectType.ts	67.07% <0.00%> (+0.80%)	⬆️

[aloisklink]

Looks good to me!

I think this approach is simpler than #5051, so it's probably better until more people are making their own custom diagrams.