[2.x] Add missing functions.

[r-kujawa]

What does this PR do? 🤖

• Adds setUp() function to PaymentResponse::class for convenience.
• Adds reset() function to PaymentService::class to help with testing.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.32% 🎉

Comparison is base (93ff20f) 66.80% compared to head (ac2085f) 67.13%.

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #39      +/-   ##
============================================
+ Coverage     66.80%   67.13%   +0.32%     
- Complexity      221      223       +2     
============================================
  Files            42       42              
  Lines           705      712       +7     
============================================
+ Hits            471      478       +7     
  Misses          234      234              

Files Changed	Coverage Δ
src/Facades/Payment.php	100.00% <ø> (ø)
src/PaymentResponse.php	58.82% <100.00%> (+3.98%)	⬆️
src/PaymentService.php	100.00% <100.00%> (ø)

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