Add basic reverse transaction logic

[matiasinsaurralde]

Based on specs defined in #52, simple tests included.
I've added a very basic HTTP handler for this action, we should ensure that errors are properly handled on a separate ticket (seems it can be improved in other handlers too).
Meta fields are still missing.

[codecov]

Codecov Report

Merging #59 (6720889) into main (d43e6f5) will increase coverage by 0.13%.
The diff coverage is 40.00%.

@@            Coverage Diff             @@
##             main      #59      +/-   ##
==========================================
+ Coverage   33.91%   34.04%   +0.13%     
==========================================
  Files          26       26              
  Lines        1374     1404      +30     
==========================================
+ Hits          466      478      +12     
- Misses        857      875      +18     
  Partials       51       51              

Impacted Files	Coverage Δ
api/http.go	0.00% <0.00%> (ø)
ledger/query/query.go	55.26% <0.00%> (-4.74%)	⬇️
core/transaction.go	100.00% <100.00%> (ø)

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