exchanges: Add Coinbase International support

[samuael]

ሰላም ወንድሞች፣

PR Description

This pull request Included a code implementation for the Coinbase International exchange version 1; with REST and web socket support. All the Websocket and Wrapper functions are tested. My code follows the style guidelines of other exchanges of GCT. Fixed all linter issues errors with the help of golangci-lint. Endpoint methods that have no support from the GCT wrapper are also implemented for future use.

• Exception in this PR: subscription to all Web-Socket channels requires authentication.
• Documentation URL: https://docs.cloud.coinbase.com/intx/docs/welcome

Fixes # (issue)

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

How has this been tested

• [x] go test ./... -race
• [x] golangci-lint run
• [x] Test X

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented on my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation and regenerated documentation via the documentation tool
• [ ] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally and on Github Actions/AppVeyor with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 26.20408% with 904 lines in your changes missing coverage. Please review.

Project coverage is 46.32%. Comparing base (98f025e) to head (b62bb26). Report is 3 commits behind head on master.

:exclamation: Current head b62bb26 differs from pull request most recent head 1edc4d5

Please upload reports for the commit 1edc4d5 to get more accurate results.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1381       +/-   ##
===========================================
+ Coverage   36.26%   46.32%   +10.05%     
===========================================
  Files         419      366       -53     
  Lines      183133   120470    -62663     
===========================================
- Hits        66421    55806    -10615     
+ Misses     108605    56996    -51609     
+ Partials     8107     7668      -439     

Files	Coverage Δ
engine/helpers.go	82.29% <100.00%> (+2.13%)	:arrow_up:
exchanges/support.go	100.00% <ø> (ø)
...seinternational/coinbaseinternational_websocket.go	23.82% <23.82%> (ø)
...ges/coinbaseinternational/coinbaseinternational.go	18.47% <18.47%> (ø)
...baseinternational/coinbaseinternational_wrapper.go	32.31% <32.31%> (ø)

... and 408 files with indirect coverage changes