Fix creating rooms when the default is set to v12

[S7evinK]

This should fix #3669
We'd potentially send an empty string to GenerateCreateContent, even if we set the correct roomVersion before.

Pull Request Checklist

• I have added Go unit tests or Complement integration tests for this PR or I have justified why this PR doesn't need tests
• Pull request includes a sign off below or I have already signed off privately

[codecov-commenter]

Codecov Report

❌ Patch coverage is 12.50000% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.26%. Comparing base (12b7038) to head (2223b61).

Files with missing lines	Patch %	Lines
federationapi/routing/threepid.go	0.00%	2 Missing ⚠️
roomserver/internal/perform/perform_peek.go	0.00%	2 Missing ⚠️
clientapi/routing/createroom.go	0.00%	1 Missing ⚠️
federationapi/routing/backfill.go	0.00%	1 Missing ⚠️
roomserver/internal/perform/perform_unpeek.go	0.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (12.50%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3670      +/-   ##
==========================================
+ Coverage   52.24%   52.26%   +0.01%     
==========================================
  Files         524      524              
  Lines       48399    48401       +2     
==========================================
+ Hits        25288    25296       +8     
+ Misses      19602    19600       -2     
+ Partials     3509     3505       -4     

Flag	Coverage Δ
unittests	52.26% <12.50%> (+0.01%)	⬆️

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[S7evinK]

Any feelings about bumping the default room version to 12? @kegsay @devonh

[devonh]

Nice fix! Surprised we haven't run into this before.

[devonh]

Any feelings about bumping the default room version to 12? @kegsay @devonh

I don't think that would be an issue. I don't have much context on how stable Dendrite is with v12. That would be my only hesitation.

[bones-was-here]

Participation in v12 rooms has been solid so far, but we haven't created many.
In a certain case gomatrixserverlib tries to parse a domain out of the room ID #3671 so probably that should be fixed before changing the default.

This patch seems to work for allowing the default to be configured to 12.

[S7evinK]

2223b61 should fix a few occurrences where we'd run in similar issues while validating the roomID.

Also, going to keep the default at v10 for now, to gather some more insights in how stable v12 is.

[bones-was-here]

Cool, that fixes #3671