Pirania rcpd api fixes and improvements

[spiccinini]

No description provided.

[codecov-commenter]

Codecov Report

Merging #892 (502af53) into master (55ec0b8) will increase coverage by 0.62%.
The diff coverage is 98.71%.

❗ Current head 502af53 differs from pull request most recent head 0cfc828. Consider uploading reports for the commit 0cfc828 to get more accurate results

@@            Coverage Diff             @@
##           master     #892      +/-   ##
==========================================
+ Coverage   73.92%   74.54%   +0.62%     
==========================================
  Files          41       43       +2     
  Lines        3559     3658      +99     
==========================================
+ Hits         2631     2727      +96     
- Misses        928      931       +3     

Impacted Files	Coverage Δ
...kages/lime-system/files/usr/lib/lua/lime/utils.lua	81.06% <75.00%> (+0.82%)	⬆️
packages/pirania/tests/pirania_test_utils.lua	100.00% <100.00%> (ø)
...-network_nodes/files/usr/lib/lua/network-nodes.lua	100.00% <100.00%> (ø)
...es/shared-state/files/usr/lib/lua/shared-state.lua	77.23% <0.00%> (+0.44%)	⬆️
...ges/pirania/files/usr/lib/lua/voucher/vouchera.lua	53.23% <0.00%> (+0.57%)	⬆️
...ckages/pirania/files/usr/lib/lua/voucher/store.lua	96.00% <0.00%> (+4.00%)	⬆️

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[germanferrero]

@spiccinini Thanks!

I had this comment about how testing of rpcd code is being done in which I proposed you to assert on lua module's add voucher method being called with the correct parameters.

But I understand that it's agile to merge this PR and change test-strategy along with the other needed changes for pirania backend.

[spiccinini]

Thanks ger for the feedback!