Allow retrieving user channels as app channels

[kriswest]

Describe your change

Fixes a check in fdc3-web-impl that was stopping user channels being retrieved via fdc3.getCurrentChannel() or fdc3.getOrCreateChannel(<channel-id>).

It also corrects an incorrectly prepared getOrCreateChannelResponse message that was using an enum for the channel type instead of the corresponding string (this did not seem to cause an issue but needed to be fixed regardless).

Related Issue

resolves #1834

Contributor License Agreement

• I acknowledge that a contributor license agreement is required and that I have one in place or will seek to put one in place ASAP.

Review Checklist

• Issue: If a change was made to the FDC3 Standard, was an issue linked above?
• CHANGELOG: Is a CHANGELOG.md entry included?

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.68%. Comparing base (c0f0e95) to head (fafabb9).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1835      +/-   ##
==========================================
+ Coverage   95.65%   95.68%   +0.02%     
==========================================
  Files          69       69              
  Lines        4631     4631              
  Branches      714      772      +58     
==========================================
+ Hits         4430     4431       +1     
+ Misses        201      200       -1     

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[kemerava]

LGTM

[kriswest]

Conflicts resolved in changelog, necessitating another review approval

[kriswest]

@finos/fdc3-maintainers pls approve

[mistryvinay]

LGTM

[kriswest]

thanks again @mistryvinay and @kemerava