message: Add buf lint in dockerfile
diff: @@ -5,8 +5,20 @@ WORKDIR /go/src/github.com/kubeapps/kubeapps
  COPY go.mod go.sum ./
  COPY pkg pkg
  COPY cmd cmd
  +
  +ARG BUF_VERSION="0.43.2"
  +RUN curl -sSL "https://github.com/bufbuild/buf/releases/download/v$BUF_VERSION/buf-Linux-x86_64" -o "/tmp/buf" && chmod +x "/tmp/buf"
  +
  # With the trick below, Go's build cache is kept between builds.
  # https://github.com/golang/go/issues/27719#issuecomment-514747274
  +RUN --mount=type=cache,target=/go/pkg/mod \
  + --mount=type=cache,target=/root/.cache/go-build \
  + go mod download
  +
  +# Lint the proto files to detect errors at build time
  +RUN /tmp/buf lint ./cmd/kubeapps-apis
  +
  +# Build the main grpc server
  RUN --mount=type=cache,target=/go/pkg/mod \
  --mount=type=cache,target=/root/.cache/go-build \
  go build ./cmd/kubeapps-apis
  