Adding grpc client

[jt-dd]

Adding the grpc client features to kubehound:

• Dumping k8s config on a bucket and then triggering the ingestion on KHaaS : ./kubehound dump cloud --bucket s3://<yourbucket> --khaas-server "127.0.0.1:9000" --insecure --debug
• Triggering a job manually on KHaaS: ./kubehound ingest --khaas-server "127.0.0.1:9000" --insecure --run_id 01htmv5zrh188fzntf8v2pc15h --cluster kind-kubehound.test.local

Two options have been added:

• khaas-server: address of the KHaaS server (ip:port)
• --insecure: to avoid dealing with the TLS madness

Since this option is shared by 2 sub commands (ingest and dump cloud), we are using the PreRunE tricks to register the same 2 flags on runtime instead of init time. Cobra does not support this for the moment:

• https://github.com/spf13/viper/issues/233

Another option has been added to the main command --debug to activate debugging mode.

Notes:

• Cleaning has been made on the viper string/config
• InitializeKubehoundConfig() has been fixed (supporting inline and config file)
• Add validator package to validate entries in KubeHound config
• Refactor a bit the system-test to support multiple ingestion (ingesting twice the same cluster without removing all data between the two stages)
• Fix race condition on tags in k8s live collector

[Minosity-VR]

After testing:

• the bucket name should be set in the configs/etc/*.yaml files, at least commented, to be able to launch the ingestor properly:

  # Ingestor configuration (for KHaaS)
  # ingestor:
  #   bucket_name: "<your-bucket>"

• The makefile could have a make build-ingestor command to help building the API CLI

  .PHONY: build-ingestor
  build-ingestor: ## Build the ingestor API CLI
  cd cmd && go build $(BUILD_FLAGS) -o ../bin/kubehound-ingestor kubehound-ingestor/*.go

• The launching of the grpc api & the commands you put in the PR description really should be in some readme, we probably even need a whole readme just for KHaas