Added captured amount to DummyProvider

[juanpsenn]

I think that this would solve #374 bug, at least for a full captured amount.
Maybe in a future consider a more complex scenario like parcial captures 🤔

What do you think? Should this be optionally?

[codecov]

Codecov Report

Merging #382 (9ab4050) into main (8455648) will decrease coverage by 0.03%.
Report is 1 commits behind head on main.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##             main     #382      +/-   ##
==========================================
- Coverage   78.54%   78.51%   -0.03%     
==========================================
  Files          29       29              
  Lines        1976     1978       +2     
  Branches      243      243              
==========================================
+ Hits         1552     1553       +1     
- Misses        308      309       +1     
  Partials      116      116              

Files	Coverage Δ
payments/dummy/__init__.py	84.90% <50.00%> (-1.37%)	⬇️

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[WhyNotHugo]

Thanks!