Add custom annotation for service

[jb-abbadie]

This will allow users of External DNS to create a record with the Pod IP of the servers.

[hashicorp-cla]

All committers have signed the CLA.

[lkysow]

Can you make it like our other service annotation keys.

service:
  # Optional YAML string for additional annotations.
   # This should be a multi-line string of
  # the annotations to apply to the server service.
  annotations: null

[lkysow]

Can you add a test to test/unit/server-service.bats similar to the mesh gateway test:

#--------------------------------------------------------------------
# annotations

@test "meshGateway/Service: no annotations by default" {
  cd `chart_dir`
  local actual=$(helm template \
      -x templates/mesh-gateway-service.yaml  \
      --set 'meshGateway.enabled=true' \
      --set 'connectInject.enabled=true' \
      --set 'client.grpc=true' \
      --set 'meshGateway.service.enabled=true' \
      . | tee /dev/stderr |
      yq -r '.metadata.annotations' | tee /dev/stderr)
  [ "${actual}" = "null" ]
}

@test "meshGateway/Service: can set annotations" {
  cd `chart_dir`
  local actual=$(helm template \
      -x templates/mesh-gateway-service.yaml  \
      --set 'meshGateway.enabled=true' \
      --set 'connectInject.enabled=true' \
      --set 'client.grpc=true' \
      --set 'meshGateway.service.enabled=true' \
      --set 'meshGateway.service.annotations=key: value' \
      . | tee /dev/stderr |
      yq -r '.metadata.annotations.key' | tee /dev/stderr)
  [ "${actual}" = "value" ]
}

[lkysow]

Suggested change

	{{- tpl .Values.server.serviceAnnotations . | nindent 4 }}
	{{- tpl .Values.server.serviceAnnotations . | nindent 4 | trim }}

[lkysow]

Thanks for the PR! Just a few comments.

[jb-abbadie]

Fixed + Rebased based on the comments.

[lkysow]

Thanks!