chore: handle missing destination in transfer protocol service

[ronjaquensel]

What this PR changes/adds

Adds a null check on the data destination to TransferProcessProtocolServiceImpl::notifyRequested before validating the destination. In requestedAction creates a destination DataAddress of type HTTP_PROXY (= pull) for the DataRequest, if no destination was specified.

Why it does that

The destination is optional according to the protocol spec, as it is only required for push transfers.

Linked Issue(s)

Closes #2728

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -53.43 ⚠️

Comparison is base (b6c5f4e) 71.91% compared to head (b5bf5b2) 18.48%.

❗ Current head b5bf5b2 differs from pull request most recent head 8883e21. Consider uploading reports for the commit 8883e21 to get more accurate results

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Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3316       +/-   ##
===========================================
- Coverage   71.91%   18.48%   -53.43%     
===========================================
  Files         810      810               
  Lines       16509    16513        +4     
  Branches      962      964        +2     
===========================================
- Hits        11872     3052     -8820     
- Misses       4236    13372     +9136     
+ Partials      401       89      -312     

Impacted Files	Coverage Δ
...ferprocess/TransferProcessProtocolServiceImpl.java	0.00% <0.00%> (-98.86%)	⬇️

... and 520 files with indirect coverage changes

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[ndr-brt]

I'd tend to avoid comments unless they are strictly necessary because they tend to rot quickly, in my opinion the unit test already describes the need for this condition.
all good otherwise.