cli: implement pending_transfers endpoint and fix /status

[andrevmatos]

Part of #1692

Short description
Title.

Definition of Done

• Steps to manually test the change have been documented
• Acceptance criteria are met
• Change has been manually tested by the reviewer (dApp)

Steps to manually test the change (dApp)

1. Test /api/v1/pending_transfers/ endpoints work as per spec

[codecov]

Codecov Report

Merging #1909 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1909   +/-   ##
=======================================
  Coverage   95.61%   95.61%           
=======================================
  Files         155      155           
  Lines        5793     5793           
  Branches     1089     1031   -58     
=======================================
  Hits         5539     5539           
  Misses        196      196           
  Partials       58       58           

Flag	Coverage Δ
#dapp	91.76% <ø> (ø)
#sdk	97.21% <ø> (ø)
#sdk_e2e	65.46% <ø> (+0.02%)	⬆️
#sdk_unit	86.51% <ø> (ø)

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[weilbith]

A complete new endpoint. 🎉
We need to take care and don't introduce inconsistencies into the code-base at already such an early stage.