Cache CMC Price Lookups

[bonedaddy]

:construction_worker: Purpose

Closes https://github.com/RTradeLtd/Temporal/issues/400 and enables an in-memory cache of cmc prices to prevent excessive requests.

:rocket: Changes

• Cache successful cmc price lookups in-memory
• When a cmc price lookup fails, return the in-memory price and error
• Within the API, ignore errors when retrieving usd prices if the returned price is non-zero

:warning: Breaking Changes

None

[xiegeo]

We could also handle temporary lookup errors over the network by reusing the old outdated value when updating the cost returns an error.

[codecov[bot]]

Codecov Report

Merging #416 into master will increase coverage by 1.22%. The diff coverage is 76.2%.

@@            Coverage Diff             @@
##           master     #416      +/-   ##
==========================================
+ Coverage   51.86%   53.08%   +1.22%     
==========================================
  Files          43       43              
  Lines        4121     4151      +30     
==========================================
+ Hits         2137     2203      +66     
+ Misses       1511     1462      -49     
- Partials      473      486      +13

Impacted Files	Coverage Δ
utils/cmc.go	70.59% <69.24%> (+3.93%)	:arrow_up:
api/v2/routes_payment.go	25.78% <87.5%> (+9.16%)	:arrow_up:
queue/ipfs_cluster.go	69.48% <0%> (+16.85%)	:arrow_up:

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[bonedaddy]

We could also handle temporary lookup errors over the network by reusing the old outdated value when updating the cost returns an error.

Good idea