Move ACS client to ecs-agent module and refactor

[danehlim]

Summary

Use ecs-agent module's wsclient in ACS, move ACS client to ecs-agent module, and refactor associated code.

Implementation details

1. In agent/acs/, swap out the following imports in all files:
   • github.com/aws/amazon-ecs-agent/agent/wsclient with github.com/aws/amazon-ecs-agent/ecs-agent/wsclient
   • github.com/aws/amazon-ecs-agent/agent/wsclient/mock with github.com/aws/amazon-ecs-agent/ecs-agent/wsclient/mock
   • github.com/aws/amazon-ecs-agent/agent/wsclient/wsconn with github.com/aws/amazon-ecs-agent/ecs-agent/wsclient/wsconn
2. Refactor agent/acs/client and move to ecs-agent/
   • agent/acs/client/acs_client.go -> ecs-agent/acs/client/acs_client.go
     • Update functions such that they conform to wsclient defined in ecs-agent module
     • Use github.com/aws/amazon-ecs-agent/ecs-agent/logger instead of github.com/cihub/seelog for logging
     • Define new empty acsClientFactory struct and refactor New() function into acsClientFactory struct method, such that acsClientFactory struct implements wsclient.ClientFactory interface
       • This wsclient.ClientFactory interface returns a new wsclient.ClientServer and helps in testing session/ACS handler code, which is critical for ACS (we can now easily test and define what to expect during session's creation of ACS client/how the ACS client came to be in the first place)
       • The size of the acsClientFactory struct itself is zero (since it contains no fields) and thus does not introduce any need for additional storage
   • agent/acs/client/acs_client_test.go -> ecs-agent/acs/client/acs_client_test.go
     • Update tests accordingly based off of changes to ACS client above
   • agent/acs/client/acs_client_types.go -> ecs-agent/acs/client/acs_client_types.go
     • Add ACS confirm attachment message to ACS recognized types
   • ecs-agent/acs/client/acs_error.go -> ecs-agent/acs/client/acs_error.go
   • ecs-agent/acs/client/acs_error_test.go -> ecs-agent/acs/client/acs_error_test.go
3. Refactor agent/acs/handler/acs_handler.go and associated files
   • agent/acs/handler/acs_handler.go
     • Account for previous implementation detail's changes to ACS client
     • Factor out over-engineered interfaces, structs, and methods related to sessionResources. Instead, simply use client factory for creating ACS client and testing the same. This results in less code that is simpler and more maintainable
   • agent/acs/handler/acs_handler_test.go
     • Update tests accordingly based off of changes to agent/acs/handler/acs_handler.go
   • agent/app/agent.go
     • Provide ACS client factory in call to acshandler.NewSession function based off of changes to agent/acs/handler/acs_handler.go

Testing

Unit, integration, and functional tests.

New tests cover the changes: yes

Description for the changelog

Move ACS client to ecs-agent module and refactor

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.