SF-3554 Create missing chapters when adding draft to a project

[RaymondLuong3]

Adding a draft to a book that is empty fails to create the missing chapters. We needed a way to detect how many chapters exist in the generated draft and notify the front end so that it can create the missing chapters and update the project texts property. This PR creates a new endpoint that can be used to get the chapters that have drafts.

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This change is 

[codecov]

Codecov Report

❌ Patch coverage is 91.22807% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.08%. Comparing base (7e21ce4) to head (8f77130).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...slate/draft-generation/draft-generation.service.ts	0.00%	3 Missing ⚠️
...draft-apply-dialog/draft-apply-dialog.component.ts	90.90%	0 Missing and 1 partial ⚠️
src/SIL.XForge.Scripture/Models/TextDocument.cs	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3432      +/-   ##
==========================================
- Coverage   82.08%   82.08%   -0.01%     
==========================================
  Files         611      611              
  Lines       36314    36355      +41     
  Branches     5966     5968       +2     
==========================================
+ Hits        29810    29843      +33     
- Misses       5641     5645       +4     
- Partials      863      867       +4     

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To fix the issue, remove the useless assignment to the local variable project while retaining the awaited call to EnsureProjectPermissionAsync. This means changing the line from SFProject project = await EnsureProjectPermissionAsync(...); to simply await EnsureProjectPermissionAsync(...);. No other code in the vicinity needs to change, and no new methods or imports are required for this fix. The edit occurs only within the scope of the method GetPretranslationChapterCountAsync in file src/SIL.XForge.Scripture/Services/MachineApiService.cs, replacing lines 1178 through 1183.

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[RaymondLuong3]

I am converting this to a draft while we move towards getting draft apply working on the backend