Build assets inside the container (#357)

Dockerfile.assets

@@ -0,0 +1,20 @@
+FROM golang:1.15 as binlayer
+
+RUN go get github.com/go-bindata/go-bindata/... && go get github.com/elazarl/go-bindata-assetfs/...
+
+FROM node:10 as uilayer
+
+WORKDIR /app
+
+COPY --from=binlayer /go/bin/go-bindata-assetfs /bin/
+COPY --from=binlayer /go/bin/go-bindata /bin/
+
+COPY ./portal-ui/package.json ./
+COPY ./portal-ui/yarn.lock ./
+RUN yarn install
+
+COPY ./portal-ui .
+
+RUN yarn install && make build-static
+
+USER node