fix(did-resolver): always include didResolutionMetadata in result

[mirceanis]

fixes #681

It looks like the did-key resolver we use does not include a didResolutionMetadata in the result.

I also deduplicated some code in sendDidCommMessage and added some more null guards.

[codecov]

Codecov Report

Merging #682 (dde8f44) into next (88264db) will increase coverage by 11.49%.
The diff coverage is 74.51%.

❗ Current head dde8f44 differs from pull request most recent head 35b7852. Consider uploading reports for the commit 35b7852 to get more accurate results

@@             Coverage Diff             @@
##             next     #682       +/-   ##
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+ Coverage   67.58%   79.07%   +11.49%     
===========================================
  Files          62       78       +16     
  Lines        1530     2361      +831     
  Branches      247      416      +169     
===========================================
+ Hits         1034     1867      +833     
- Misses        400      492       +92     
+ Partials       96        2       -94