Add fiat endpoints

[pcasteran]

Add the fiat endpoints:

• Fiat Deposit/Withdraw History : /sapi/v1/fiat/orders
• Fiat Payments History : /sapi/v1/fiat/payments

[codecov]

Codecov Report

Merging #337 (54c8faf) into master (b9a21fe) will decrease coverage by 0.49%.
The diff coverage is 36.84%.

@@            Coverage Diff             @@
##           master     #337      +/-   ##
==========================================
- Coverage   73.69%   73.19%   -0.50%     
==========================================
  Files          59       60       +1     
  Lines        5561     5637      +76     
==========================================
+ Hits         4098     4126      +28     
- Misses       1084     1120      +36     
- Partials      379      391      +12     

Impacted Files	Coverage Δ
v2/fiat_service.go	33.33% <33.33%> (ø)
v2/client.go	84.14% <100.00%> (+0.26%)	⬆️

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