Migrate KFServing to Go Module (kserve#796)

* delete vendor

* Fix codegen

* Add go mod

* Fix status map type

* Fix status test

* Fix url address

* Fix url address test

* Pin controller tools version

* Remove address hack

* Fix dockerfile for go mod

* Update generated code

* Fix unit tests

* Fix dockerfile

* Fix openapi gen

* Copy go mod file

* Remove resource validation

* Increase timeout

* Add comment for update-codegen.sh

* Fix controller gen version

* Update api docs

* Remove generate from test target

* Update developer guide for GO MOD

* Fix rbac role name

* Add object selector

* Fix addressable type

* Fix addressable type

* Fix status map

* Generate swagger.json

* Fix status validation

* Review comments

* Clean up dependency

Dockerfile

@@ -4,9 +4,11 @@ FROM golang:1.13.0 as builder
 # Copy in the go src
 WORKDIR /go/src/github.com/kubeflow/kfserving
 COPY cmd/    cmd/
-COPY vendor/ vendor/
 COPY pkg/    pkg/
+COPY go.mod  go.mod
+COPY go.sum  go.sum
 
+RUN  go mod download
 # Build
 RUN if [ "$(uname -m)" = "ppc64le" ]; then \
         CGO_ENABLED=0 GOOS=linux GOARCH=ppc64le go build -a -o manager ./cmd/manager; \
@@ -17,7 +19,7 @@ RUN if [ "$(uname -m)" = "ppc64le" ]; then \
     fi
 
 # Copy the controller-manager into a thin image
-FROM ubuntu:latest
+FROM gcr.io/distroless/static:latest
 WORKDIR /
 COPY third_party/ third_party/
 COPY --from=builder /go/src/github.com/kubeflow/kfserving/manager .