fix: #1053 Base64URLSafe padded and unpadded decoding

[lukewli-anonyome]

This PR introduces a fix for the Base64URL encoding/decoding outlined in issue #1053.

Closes #1053

[codecov-commenter]

Codecov Report

Attention: 23 lines in your changes are missing coverage. Please review.

Comparison is base (882529c) 0.05% compared to head (e55d957) 0.05%.
Report is 11 commits behind head on main.

Files	Patch %	Lines
aries/aries_vcx/src/common/signing.rs	0.00%	23 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #1083      +/-   ##
========================================
- Coverage   0.05%   0.05%   -0.01%     
========================================
  Files        471     471              
  Lines      24009   24109     +100     
  Branches    4306    4336      +30     
========================================
  Hits          13      13              
- Misses     23995   24095     +100     
  Partials       1       1              

Flag	Coverage Δ
unittests-aries-vcx	0.05% <0.00%> (-0.01%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Patrik-Stas]

Hi @lukewli-anonyome! Thank you for the contribution! George will handle the review here, apart from warm welcome just one small tip:
The CI is failing on formatting, you can always easily verify formatting running cargo +nightly-2023-05-08 fmt --check and fix the formatting as follows. cargo +nightly-2023-05-08 fmt --check.
We have currently hardcoded this particular nightly version of rust for formatting verification in CI, hence the strange looking command ;-)

[gmulhearn-anonyome]

nice, thanks for the effort!