[FEATURE] `command`, `tcpSocket` and `grpc` `livenessProbe` and `readinessProbe` support

[mathieu-benoit]

Detailed description

It would be ideal to support the command, tcpSocket and grpc methods for livenessProbe and readinessProbe.

Context

Today, only the httpGet method for livenessProbe and readinessProbe is supported.

command is another very popular method, like illustrated here with grpc apps: https://github.com/GoogleCloudPlatform/microservices-demo/blob/main/release/kubernetes-manifests.yaml#L61.

So for example, today, this below is not supported:

apiVersion: score.dev/v1b1
metadata:
  name: adservice
containers:
  adservice:
    image: gcr.io/google-samples/microservices-demo/adservice:v0.6.0
    variables:
      PORT: "9555"
    livenessProbe:
      exec:
        command:
          - /bin/grpc_health_probe
          - '-addr=:9555'
    readinessProbe:
      exec:
        command:
          - /bin/grpc_health_probe
          - '-addr=:9555'

Possible implementation

Humanitec already supports tcpSocket and command in addition to httpGet.

Note: gRPC (only supported since Kubernetes 1.24+) is not yet supported in Humanitec. The alternative is to use the command method by using the grpc_health_probe binary.

Additional information

Configure Liveness, Readiness and Startup Probes in Kubernetes.