Challenge response flow

[pfeairheller]

This PR includes:

• Added necessary endpoints to complete the challenge response flow.

[codecov]

Codecov Report

Merging #111 (bef2426) into development (42c6288) will increase coverage by 0.05%.
The diff coverage is 97.10%.

@@               Coverage Diff               @@
##           development     #111      +/-   ##
===============================================
+ Coverage        91.68%   91.73%   +0.05%     
===============================================
  Files               35       35              
  Lines             5543     5601      +58     
===============================================
+ Hits              5082     5138      +56     
- Misses             461      463       +2     

Files	Coverage Δ
src/keria/app/aiding.py	85.45% <100.00%> (+0.41%)	⬆️
tests/app/test_aiding.py	100.00% <100.00%> (ø)
tests/app/test_specing.py	100.00% <ø> (ø)
src/keria/core/longrunning.py	70.74% <88.88%> (+1.40%)	⬆️

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