fix(SaveService): Don't save if yjs reports pendingStructs

[mejo-]

Yjs pendingStructs mean that the local yjs document state is missing a step. So let's not allow to save such an inconstent state to the server.

Screenshot

Disabled save button

🏁 Checklist

• Code is properly formatted (npm run lint / npm run stylelint / composer run cs:check)
• Sign-off message is added to all commits

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.55%. Comparing base (07cc286) to head (28ee3e7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7704      +/-   ##
==========================================
+ Coverage   59.52%   59.55%   +0.03%     
==========================================
  Files         503      503              
  Lines       39118    39150      +32     
  Branches     1130     1130              
==========================================
+ Hits        23285    23317      +32     
  Misses      15725    15725              
  Partials      108      108              

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[max-nextcloud]

Waiting for the outcome of our attempts to prevent out of sync state and thus pending structs in the first place.