Change actorID to be non-optional

[chacha912]

What this PR does / why we need it?

When creating a document, the InitialChangeID is used as the ChangeID, ensuring that there are no cases where actorID is undefined.
Therefore, the actorID of ChangeID and TimeTicket always exists, making it non-optional.

Any background context you want to provide?

What are the relevant tickets?

Fixes #552

Checklist

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (e636b3e) 81.22% compared to head (c17f4b4) 81.33%.

Files	Patch %	Lines
src/document/change/change_id.ts	0.00%	1 Missing ⚠️
src/document/document.ts	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #747      +/-   ##
==========================================
+ Coverage   81.22%   81.33%   +0.11%     
==========================================
  Files          59       59              
  Lines        4292     4286       -6     
  Branches      839      836       -3     
==========================================
  Hits         3486     3486              
+ Misses        547      543       -4     
+ Partials      259      257       -2     

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[hackerwins]

Thanks for your contribution.