Add overloaded signing util methods

[josephtaylor]

New IPKSigningUtil methods and implementation in both PKFileBasedSigningUtil
and PKInMemorySigningUtil that allow callers to provide an OutputStream that
the signed pass will be written to.

This allows callers to stream the output wherever they want without
holding the entire signed pass in memory as a byte array.

[CLAassistant]

All committers have signed the CLA.

[drallgood]

ooh.. I like that idea. Thanks @josephtaylor

[drallgood]

@josephtaylor could you please pull in main again? I fixed the certificate error so tests should pass now

[josephtaylor]

@drallgood apologies for the delay here, just got main merged down into the branch

[drallgood]

LGTM ✅
Nice improvement adding OutputStream-based signing overloads. This is a meaningful API enhancement for memory-sensitive paths and streaming use cases, and the change appears additive/backward-compatible.

I especially like that this is implemented across both signing util implementations so behavior stays consistent regardless of backing strategy.

Nits / follow-ups (non-blocking):

Please ensure Javadocs clearly define stream ownership (whether the callee closes the provided OutputStream).
If not already covered, add/confirm tests that verify parity between byte-array and stream overload outputs.
Consider a targeted large-pass test to validate the intended memory benefit path.

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Codecov Report

❌ Patch coverage is 81.81818% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.28%. Comparing base (d48443d) to head (1ce89c8).

Files with missing lines	Patch %	Lines
...amour/jpasskit/signing/PKPassTemplateInMemory.java	42.85%	4 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##               main     #649      +/-   ##
============================================
- Coverage     81.37%   81.28%   -0.09%     
- Complexity      749      753       +4     
============================================
  Files            59       59              
  Lines          1648     1662      +14     
  Branches         58       58              
============================================
+ Hits           1341     1351      +10     
- Misses          255      259       +4     
  Partials         52       52              

Flag	Coverage Δ
unittests	81.28% <81.81%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...amour/jpasskit/signing/PKFileBasedSigningUtil.java	71.08% <100.00%> (+1.46%)	⬆️
...damour/jpasskit/signing/PKInMemorySigningUtil.java	69.69% <100.00%> (+2.48%)	⬆️
...amour/jpasskit/signing/PKPassTemplateInMemory.java	93.44% <42.85%> (-6.56%)	⬇️

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