Change RepoConfig.GPGKey to an array of key strings

DNF supports more than one GPG key. It is possible that one may be used for
signing packages, and another to sign the repository metadata. This
renamed GPGKey to GPGKeys internally. It does not change the on-disk
repository json format.

cmd/gen-manifests/main.go

@@ -187,12 +187,17 @@ func makeManifestJob(name string, imgType distro.ImageType, cr composeRequest, d
 type DistroArchRepoMap map[string]map[string][]repository
 
 func convertRepo(r repository) rpmmd.RepoConfig {
+	var keys []string
+	if r.GPGKey != "" {
+		keys = []string{r.GPGKey}
+	}
+
 	return rpmmd.RepoConfig{
 		Name:           r.Name,
 		BaseURL:        r.BaseURL,
 		Metalink:       r.Metalink,
 		MirrorList:     r.MirrorList,
-		GPGKey:         r.GPGKey,
+		GPGKeys:        keys,
 		CheckGPG:       r.CheckGPG,
 		MetadataExpire: r.MetadataExpire,
 		ImageTypeTags:  r.ImageTypeTags,

cmd/osbuild-pipeline/main.go

@@ -140,12 +140,18 @@ func main() {
 		if repoName == "" {
 			repoName = fmt.Sprintf("repo-%d", i)
 		}
+
+		var keys []string
+		if repo.GPGKey != "" {
+			keys = []string{repo.GPGKey}
+		}
+
 		repos[i] = rpmmd.RepoConfig{
 			Name:        repoName,
 			BaseURL:     repo.BaseURL,
 			Metalink:    repo.Metalink,
 			MirrorList:  repo.MirrorList,
-			GPGKey:      repo.GPGKey,
+			GPGKeys:     keys,
 			CheckGPG:    repo.CheckGPG,
 			PackageSets: repo.PackageSets,
 		}