pkg/asset/installconfig: Add OPENSHIFT_INSTALL_AWS_USER_TAGS

With a JSON string containing the intended values.

This is probably not how we're going to expose this long-term, so I'm
not documenting the enviroment variable yet.  But I want this so we
can get back to tagging expirationData in CI, without waiting for
asset state <-> disk (de)serialization.

pkg/asset/installconfig/platform.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/url"
+	"os"
 	"sort"
 	"strings"
 
@@ -162,6 +163,12 @@ func (a *Platform) awsPlatform() (*asset.State, error) {
 	}
 	platform.Region = string(region.Contents[0].Data)
 
+	if value, ok := os.LookupEnv("OPENSHIFT_INSTALL_AWS_USER_TAGS"); ok {
+		if err := json.Unmarshal([]byte(value), &platform.UserTags); err != nil {
+			return nil, fmt.Errorf("OPENSHIFT_INSTALL_AWS_USER_TAGS contains invalid JSON: %s (%v)", value, err)
+		}
+	}
+
 	data, err := json.Marshal(platform)
 	if err != nil {
 		return nil, err